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RADIO THEORY 
SIMPLIFIED 


A RADIO DICTIONARY 












. • 













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•• 


•• 4 

: 




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' 
















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\ 





RADIO THEORY 
SIMPLIFIED 

WITH 

A RADIO DICTIONARY 


BY 

MERLE DUSTON 

AUTHOR OF 

"RADIO CONSTRUCTION FOR THE AMATEUR” 
AND OTHER RADIO BOOKS 


Illustrated by 

DOUGLAS G. HAWKSWORTH 


^^hitmatTTubushing Co. 

RACINE. WISCONSIN 


1 Ktrso 

■ Dess 


Copyright 1924 by 
Duston Radio Laboratories, Inc. 


Printed in U. S. A. 



5 ? 

OCT 15 1924 

©C] A 807371 

l 




This book is respectfully dedicated to 
our friend: THE RADIO FAN whose 
desire for a more thorough knowledge of 
Radio, we believe, justified us in the com¬ 
pilation of this book. 






PREFACE 



N O EXCUSES are offered for the publication of this 
book. This book was written primarily for persons 
who are in the class known as the “Broadcast Lis¬ 
tener.” There have been many good books written that 
could be understood by anyone not wishing to take the 
time or the pains to really study the theory of Radio 
Transmission and Reception, but it is believed that in 
proportion to the number of people interested, these 
books are all too few. 

If the subject be considered, it will be found that most 
of the books dealing with radio were written for the man 
who has applied or was willing to apply himself to the 
study of Radio in all its phases, and would concentrate 
his mind on the subject at hand. Consequently he could 
use a book which dealt with details regarding the more 
technical questions. 

In this book, the intention has been merely to hit the 
high spots of Radio Theory, clearly defining and explain¬ 
ing sufficient subjects so that the Amateur who wishes to 
build or buy a Radio Receiving Set will have ample 
knowledge of the various types of sets and parts. He can 
then buy only those which will best fit his needs. It has 
been the aim to use comparison^ of objects familiar to the 


reader, but as radio waves are understood to be different 
in certain respects from other types of waves, these com¬ 
parisons are used cautiously; however, it is hoped that 
the matter herein contained will give the reader a fair 
understanding of the underlying principles of Radio 
Transmission and Reception. 

Some of the theories advanced will probably be dis¬ 
agreed with but as radio has had such a rapid growth and 
as comparatively little is known about it, criticisms are 
to be expected. 

As this is the first edition of the book, the Author will 
be glad to have any errors or omissions called to his 
attention. 

The Author also wishes to extend credit and express 
his appreciation to Prof. Harry' O. Warner of the Electrical 
Engineering Department of the University of Detroit; 
and his co-workers, Theodore Schmalzriedt, Jr. and 
Douglas G. Kawksworth, for the many helpful suggestions 
which they gave in the compilation of this book. 

THE AUTHOR, 
Detroit, Mich., July 1, 1924. 


10 


TABLE OF CONTENTS 


CHAPTER I. RADIO WAVES 
EXPLAINED 

Page 

1. Ohms Law. 19 

2. Ether Waves. 21 

3. Ether. 22 

4. Radio Waves. 22 

5. Frequency of Radio Waves. 23 

6. Sound Waves. 29 

7. Harmonics. 31 

8. Damped Waves.31 

9. Transmitting Stations. 33 

CHAPTER II. TRANSMITTING AND RECEIVING AERIALS 

10. Use of the Aerial. 37 

11. Loop Aerials. 40 

12. Tuning the Antenna.... 41 

CHAPTER III. THE OPERATION AND ACTION OF CRYSTAL 
DETECTORS AND AUDION BULBS 

13. Rectification of Radio Frequency Waves. 45 

14. Crystal Detector Rectifier..46 

15. The Audion Bulb.-.46 

16. The Electron Theory. 47 

17. The Two Element Bulb.49 

18. The Three Element Bulb.... —.SO 

19. Grid Condenser and Leak.54 

20. Audio Frequency Amplification.-.56 

21. Audion Bulbs used for Amplification of Radio Frequency Waves.59 

21A Aud ion Bulb used as a Generator of High Frequency Currents.60 

CHAPTER IV. RECEIVING SETS 

22. Facts about Receiving Sets. 62 

23. Theory of Regeneration.64 

24. Re-radiation of Regenerative Sets.65 

25. Single Coil Crystal Set. 6 ' 

26. Two Coll Crystal Set.68 

27. Single Circuit non-regenerative Set..• • 69 

28. Two Circuit non-regenerative Set. 70 

29. Single Circuit Regenerative Set.:..•. 72 


11 


































30. Three Circuit Regenerative Set. 74 

31. The Reinartz Receiver.77 

32. Neutrodyne Sets. 78 

33. Reflex Circuits.80 

34. Audio Frequency Amplifiers.81 

35. Super-heterodyne.82 

36. The Acmedyne Circuit.84 

37. Inverse Duplex.86 

38. Radio Frequency Amplifiers 

(Transformer Coupled).90 

39. Radio Frequency Amplifiers.90 

(Tuned) 

40. Power Amplifiers.92 

CHAPTER V. USE OF PARTS IN RECEIVING SETS 

41. "A" Battery.94 

42. Aerial Insulator.96 

43. Aerial Wire.96 

43A “B” Batteries.97 

44. *‘B” Batteries (chargeable).98 

45. Battery Chargers.99 

46. Bezels.100 

47. “C" Batteries.101 

48. Choke Coils.101 

49. Condensers (Fixed).101 

50. Condensers (Variable).102 

51. Crystal Detector.103 

52. Dials.104 

53. Grid Condensers.105 

54. Grid Leaks.105 

55. Ground Clamps. 106 

56. Honeycomb Coils.107 

57. Hydrometers.108 

58. Inductance Switches.108 

59. Jacks.109 

60. Loose Couplers.110 

61. Loop Antennae.Ill 

62. Loud Speaking Units.112 

63. Panel Markers.114 

64. Plugs. 115 

65. Potentiometers.115 

66. Resistance Units.116 

67. Rheostats. 117 

68. Sockets.118 

69. Socket Brackets. 119 

70. Soldering Lugs. 119 

71. Spiderweb Coils.».120 

72. Transformers (Audio Frequency).121 

73. Transformers (Radio Frequency).123 


12 















































74. Vario-Couplers. ^24 

75. Variometers.. 

76. Bulbs used in Receiving Sets. 125 

77. Radiotron UV 199 and Cunningham C 299. 126 

78. Radiotroa UV 201 and Cunningham C 301. 128 

79. Radiotron UV 201A and Cunningham C 301A.128 

80. Radiotron WD 11 or Cunningham Cll.130 

81. Radiotron WD 12 or Cunningham C 12. 131 

82. Northern Electric 215-A Bulb. 133 

83. Western Electric 216-A Bulb. 135 

CHAPTER VI. HISTORY OF RADIO ADVANCEMENT 1827-1924 137 
APPENDIX “A” USEFUL TABLES AND CHARTS 157 


Table of Abbreviations. 

Symbols used In Radio Diagrams. 

Copper Wire Table. 

Common Radio Abbreviations. 

International Telegraphic Code. 

Table showing relation of wave length to frequency. 

International Radlotelegraphic List of Abbreviations. 

APPENDIX “B” 169 

The Amateur Radio Operator and the A.R.R.L. 

The necessity for a better understanding between the broadcast listener and the 
Amateur Radio Operator. 

APPENDIX “C” LOCATING TROUBLE IN RECEIVING SETS 175 
Hints on how to find the trouble if set fails to operate at all. 

Hints on how to find the trouble if noises can be beard in set but no signals can be 
received. 

Hints on how to find the trouble if weak signals can only be received. 

Hints on how to find the trouble when noises are present with signals. 

How to find cause of distorted signals. 

INDEX—COMPLETE TO COVER SUBJECTS AND 

ITEMS DISCUSSED IN BOOK 178 

PART II 

A RADIO DICTIONARY OF RADIO TERMS AND WORDS 185 


13 





















LIST OF ILLUSTRATIONS 


Figure 

1. Water Analogy used to explain Ohms Law. 

2. Electrical Resistance compared to Resistance in water pipe. 

3. Amplitude and wave-length measurement of un-damped wave. 

4. Amplitude and wave-length measurement of damped wave. 

5. Change in amplitude of modulated wave. 

6. Direct flow of water compared to direct flow of electricity. 

7. Alternating flow of water compared to alternating current of 
electricity. 

8. Radio wave with frequency of one cycle per second. 

9. Radio wave with frequency of ten cycles per second. 

10. Radio wave with frequency of thirty cycles per second. 

11. Undamped waves explained. 

12. Damped waves explained. 

13. Series of damped wave trains. 

14. Transmission and reception of continuous radio waves, 

15. Transmission and reception of radio waves. 

16. Large metal plates could be used as antenna. 

17. Antenna using ground as one side of condenser. 

18. Antenna using counterpoise as one side of condenser. 

19. Inefficient aerial having trees, buildings, etc. in condenser field. 

20. Tuning the antenna by using tapped coil and variable con¬ 

denser. 

21. Method of using tapped coil between aerial and ground. 

22. Method of using variable condensers to tune fixed coils. 

23. Crystal detector rectification of radio waves. 

24. Electron flow between filament and plate. 

25. Circuit using two element bulb. 

26. Water anology showing use of grid. 

27. Action of three element bulb when grid is positive. 

28. Action of three element bulb when grid is negative. 

29. Modulated radio wave train. 

30. Modulated wave. 

31. Circuit showing transformer coupled audio frequency amplifier. 

32. Circuit showing resistance coupled audio frequency amplifier. 


15 



33. Circuit showing transformer coupled radio frequency amplifier. 
33A Effect of Radio frequency amplification. 

34. Original Armstrong Regenerative circuit. 

35. Theoretical operation of crystal detector circuit 

36. Crystal detector circuit. 

37. Two coil crystal detector circuits. 

38. Single circuit non-regenerative hook-up. 

39. Two coil non-regenerative circuits. 

40. Theoretical operation of single circuit regenerative set 

41. Vario-coupler single circuit regenerative hook-up. 

42. Two coil single circuit regenerative hook-up. 

43. Standard three circuit receiver. 

44. Three coil regenerative receiver. 

45. Original Reinartz Circuit. 

46. Five bulb Neutrodyne Receiver. 

47. Drawing showing Reflex action of bulbs. 

48. Two bulb Reflex Circuit. 

49A Condensed drawing of super-heterodyne. Note: Radio 
frequency amplifier unit generally consists of three bulbs and 
audio frequency unit of two. 

49B Super-Heterodyne lay-out. 

50. Four bulb Acmedyne Circuit. Note: Also known as Tele- 

monic Circuit. 

51. Drawing showing inverse duplex action of bulbs. 

52. Three bulb Grimes inverse Duplex Circuit. 

53. Un-tuned transformer coupled radio and audio frequency cir- 

cpit. 

54. Tuned radio frequency five bulb circuit. 

55. Two bulb push-pull amplifying unit. 

56. Radio “A’' storage battery. 

57. Aerial insulator. 

58. Dry “B" battery. 

59. Storage “B” battery. 

60. Storage “A” and “B” battery charger. 

61. Ventilator or bezel. 

62. "C" battery. 

63. Fixed condenser. 

64. Variable condenser. 

65. Crystal detector. Adjustable. 

66. Dial. 


16 


67. Grid condenser. 

68. Grid leak. 

69. Ground clamp. 

70. Honeycomb or Duolateral coil. 

71. Hydrometer or storage battery tester 

72. Inductance switch. 

73. Jacks. 

74. Loop antenna. 

75. Loud speaker or radio horn. 

76. Phonograph loud speaking attachment. 

77. Panel markers. 

78. Phone plug. 

79. “A” battery potentiometer. 

80. Resistance Unit. 

81. Filament Rheostat. 

82. Tube sockets. 

83. Socket and transformer brackets. 

84. Soldering lugs. 

85. Spiderweb coil. 

86. Audio frequency transformer. 

87. Radio frequency transformer. 

88. Vario-coupler. 

89. Variometer. 

90. UV 199 or C 299 audion bulb. 

91. Hook-up showing proper place for “C" or Grid Bias Battery. 

92. Hook-up showing proper connections for grid return. 

93. UV 200 or C 300 audion bulb. 

94. WD 11 or C 11 audion bulb. 

95. WD 12 or C 12 audion bulb. 

96. Northern Electric type 215A audion bulb. 

97. Western Electric type 216A audion bulb. 


U 











CHAPTER L 

RADIO WAVES EXPLAINED 

1. OHMS LAW. The most commonly known and 
understood law of electricity is Ohms Law. As this law 
can only be applied thoroughly to direct current, it has a 
limited application in radio work in which A. C. (alter¬ 
nating current) is mostly used; but in order that the 
reader may not become confused between what might be 
his understanding of electricity and the high frequency 
waves used in radio, a short illustration of Ohms Law 
will be given. 

Referring to Fig. 1, there are two large tanks—one of 
these is filled with water and the other is empty. To 
transmit this water it is necessary to have the pipe shown 
at ' A” and the pump, or generator, shown at “B.” The 
rate at which the water flows through the pipe, applied 
in electrical terms, would be the “Current” or “Amperes.” 




or wrn£& BnprrY tq/vk 

pig. I— Water Analogy Used to Explain Ohms Law. 


19 

























20 


RADIO THEORY SIMPLIFIED 


The number of pounds pressure on the pipe would corre¬ 
spond to the volts. (This is also called Electromotive 
Force, E. M. F.) The resistance to the flow of water 
through the pipe is called “resistance” and is measured 
in Ohms. By this can be seen that if the quantity of any 
two of these are known, the other can be found. This 
can also be explained by referring to Fig. 2. Here there 
is a water pump connected to a pipe, a pressure gauge 
showing the pounds of pressure available at station “A.” 
There is also a meter which shows the rate of flow of the 
water through the pipe. There is also the same pressure 
gauge at station “B.” The resistance of the pipe and 
'the amount of power lost in transmission can then be 
determined. The pressure gauge can be compared to a 
volt meter, and the flow meter would show the amount 
of current the same as an Ammeter. The power expended 
to overcome friction resistance in the pipe is lost the same 
as some power is lost to overcome resistance when using 
electricity. If this principle is understood it can be 
applied to some parts used in a radio set. 

From the above it can be seen that: 

E.M.F. or Volts 

Ohms or Resistance=--— 

Amperes or Current 


/yasssc/gc Gauoc. pressure 



Fig. 2—Electrical Resistance Compared to Resistance in Water Pipe. 











RADIO THEORY SIMPLIFIED 


The following symbols are generally used in working 
out formulae by Ohms Law: “R" stands for Resistance; 
"E” for Electromotive Force and “I” for Amperes or 
current, so that 

R=— 1=^ E=I x R 

I R 

A Potentiometer has so many ohms resistance, say 200 
or 600 ohms. Reference will again be made to these in 
the chapter where they will be taken up individually. 

In Chapter Five will also be explained what is meant 
by the number of Amperes which it takes to operate 
certain types of bulbs. 



Fi&. 3—Amplitude and Wave-length Measurement of Un-damped Wave. 


2. ETHER WAVES: The first questions that arise 
in the mind of the beginner in radio are: “how and what 
are radio waves; how are they made; how do they travel; 
and how can they be used?” There are many kinds of 
waves; such as, Heat Waves, Light Waves, Ultra-Violet 
Waves, X-Ray Waves and several unknown Waves as 
well as Radio Waves, in which we are most interested. 
Light Waves and Radio Waves are the same insofar as 
they travel at the speed of 186,000 miles per second. 










22' 


RADIO THEORY SIMPLIFIED 


3. ETHER: All of the above waves travel through 
what is known as Ether (has no connection with the 
chemical of the same name.) Now just what the Ether 
is or its extent is a question which the most eminent 
scientists of the day cannot decide. Suffice then to know 
it is some means in nature which carries Radio Waves, 
and this Ether is everywhere; inside the earth, outside 
|the earth, and between the planets. It is known that 
.there is some power which controls the universe and 
although the extent of this power is unknown, one sees 
His manifestations and a name is given Him. So the 
same can be said of that which carries Radio Waves. 
Exactly what it is, is unknown; but it is known to be 
there and we know some of its activities, so it is given a 
name and that name is “ ETHER.'* 



4. RADIO WAVES: The Radio Transmitting Sta¬ 
tions set up a wave in the Ether the same as a wave could 
be set up in a body of water by throwing a stone, or some 
other object, into the water. These waves can be of dif¬ 
ferent lengths just as the wave in a body of water can be 
of different lengths. Waves are measured as shown in 
Figs. 3 and 4.. (Remember this, That the length of the 
wave can remain the same and the amplitude or height, 








RADIO THEORY SIMPLIFIED 


2 $ 


change ); so that Fig. 5 illustrates such a wave train. How 
this wave train is obtained will be shown later in the 
chapter. 

5. FREQUENCY OF RADIO WAVES: A con¬ 
tinuous or direct current is one which does not change its 
polarity, but travels in a given direction at all times. In 
an alternating current we have what is known as Fre¬ 
quency. As the electricity changes from positive to neg¬ 
ative, one complete revolution or change is called a cycle. 
In Fig. 6 and Fig. 7, a water analogy is used to explain 
the difference between an alternating and direct current. 
In Fig. 6 a water pump is connected to a pipe line in which 
is installed a water motor. The water is always flowing 
in one direction and consequently the forces are applied 



to the water motor in the one direction and it always 
turns the same way. Now in Fig. 7 a different type of 
pump is used, which first forces the water in one direction 
and then forces it in the other. This alternating in the 
directional flow of water will also force the water motor 




























24 


RADIO THEORY SIMPLIFIED 


in one direction for a certain period of time and then re¬ 
verse it and force it in the other direction. Comparing 
this again to electricity, it is the same with an alternating 
current. When starting the cycle the piston forces the 
water in one direction and then back in the other, thus 
completing the cycle. This cycle or motion of an elec- 



Fig. 6—Direct Flow of Water Compared to Direct Flow of Electricity. 

trical wave can be indicated by a curve such as is shown 
in Fig. 7. In this book, as well as in most other Radio 
and Electrical books, these curves are used to designate 
different types of radio and electrical waves and their 
frequencies, and it is therefore best to have a thorough 
understanding of just what they mean. Now, in the 




















RADIO THEORY SIMPLIFIED 


25 



alternating current, the occurrence of the loops in the 
wave train is so rapid that it is not noticeable when used 
for lighting up a bulb. Although the current changes 
back and forth from positive to negative and at times 
there is a zero point, this does not cause a flickering of the 



Fig. 7—Alternating Flow of Water Compared to Alternating Current of Electricity. 

light because this change occurs so quickly that the fila¬ 
ment of the light does not have a chance to become cool 
between cycles or changes. 

Alternating current motors are so constructed that the 
armature, or rotor, does not reverse with the current but 
































































26 


RADIO THEORY SIMPLIFIED 


travels in one general direction. This is the reason that, 
outside of the universal type motors the same motor will 
not work on both alternating and direct current. The 
ordinary alternating electricity used for lighting pur¬ 
poses has sixty (60) complete cycles in a second, and in 
radio work it sometimes changes as rapidly as five million 
times a second. 

To many persons one of the most confusing questions 
is the difference between the frequency of waves in cycles 
or kilocycles, and their length in meters. Just recently 
the United States Government has made a change in the 



Fig. 8—Radio Wave with Frequency of One Cycle per Second. 


way it designates radio stations. It used to be that a 
station was assigned a certain wave length, where now 
the station is rated in the number of kilocycles. Referring 
to Figs. 8, 9, and 10, the difference between the lines “A” 
and “B” is 186,000 miles, or, when spoken of in the metric 
system, approximately 300,000,000 meters. Now the 
distance between “A” and “B”, which is the distance 
that electricity travels in one second, will always remain 
the same, whereas,the distances between the waves will 
change in comparison to the number of these that are 






















RADIO THEORY SIMPLIFIED 


27 


sent out per second. In Fig. 8 we send out one wave per 
second, which would have a wave length of 300,000,000 
meters. In Fig. 9 ten of these are sent out per second and 
they each have a wave length of 30,000,000 meters. In 



Pig. 9—Radio Wave with Frequency of Ten Cycles per Second. 


Fig. 10 thirty of these are sent out per second and they 
each have a wave length of 10,000,000 meters. The 
frequency of this wave would be thirty cycles per second. 
For amateur and broadcast transmission such a great 
number of these is used per second that instead of desig¬ 
nating them in the number of cycles per second, they 
speak of them as the number of kilocycles per second. 
(A kilocycle is 1,000 cycles.) From the foregoing it will 



























28 


RADIO THEORY SIMPLIFIED 


be easily understood that the more of these changes, or 
cycles, that are sent out per second, the shorter will be 
the length of the wave. To get the length of any wave in 
meters, divide the constant 299,820 by the number of 
kilocycles given. 



Another comparison that can be used would be to 
think of an imaginary train. This train is traveling at 
the speed of 186,000 miles per second. The cars that are 
in this train will be compared to frequency, or cycles, and 
the length of the cars can be compared to the wave length. 
Now if it is desired to know the frequency, count the 
number of cars in 186 000 miles. Then to obtain the 
wave length, measure the length of one car. The wave 
length or frequency of a transmitter has nothing to do 
with the distance that the stations can be heard. The 
reason for this will be explained later. 






































































RADIO THEORY SIMPLIFIED 


29 


6. SOUND WAVES: Sound waves have a major 
part in Radio Telephony, therefore an explanation of 
some of the characteristics of sound will be given. There 
are sound waves, which regardless of the much discussed 
subject, do not have to have the presence of an ear as 
evidence of sound. Sound waves have frequency and 
wave length just the same as a radio wave, but the length 
of the wave and the distance that it will travel through 
the air depends upon the temperature and other variables, 1 
where this does not hold true with radio waves. 



Anyone in the back of a hall listening to a speech or 
sermon delivered by a speaker, the speaker being close to 
a microphone which is connected to a broadcasting sta¬ 
tion, will hear the voice of the speaker a fraction of a 
second after any person who is listening to the same 
speaker over the radio, although the radio listener may 
be over 1,000 miles distant. As radio waves travel at 
the rate of 186,000 miles per second and a sound wave, at 
ordinary temperature, travels only 1,100 feet per second, 
it will be seen that there is quite a difference. 













30 


RADIO THEORY SIMPLIFIED 


There are audible and inaudible sound waves the same 
as we have a high frequency and low frequency in radio 
waves. Also with sound waves; they will travel through 
certain solids better than through the air. This same 
holds true with an electrical wave, only an electrical wave 
follows a wire at the same speed as it travels through the 
Ether, where a sound wave travels faster through a solid 
conductor than it does through space. Sound waves are 
affected by the wind, whereas radio waves are not. In 
sound waves there exists that which is called Harmonics, 
which causes a reflection of the voice of a friend to be 
recognized. In radio exists also Harmonics of a radio 
station. 



Fig. 13—Damped Waves Explained. 










RADIO THEORY SIMPLIFIED 


31 


7. HARMONICS: These axe over-tones or under¬ 
tones which give the reflection to the human voice and 
give quality or timbre to a musical sound. The Har¬ 
monics are an exact multiple of the fundamental fre¬ 
quency of the sound wave. In radio there exists also a 
harmonic frequency, which is also an exact multiple of 
the transmitted wave. These harmonics are undesirable 
in radio transmission and cannot be wholly done away 
with, but are kept down to a m nimum. This is the 
reason one sometimes hears a station on an altogether 
different wave length or frequency from that being trans¬ 
mitted, as well as being able to hear it on the basic fre¬ 
quency. 

8. DAMPED WAVES: In radio communication 
there is also used what is known as a damped wave. These 
can best be explained by referring to Figs. 11 and 12. 
Here a ball suspended on a string is being moved back 
and forth. Now if each time this ball swings back and 
forth, we applied the same force to the ball, it would 
swing in the same cycle as shown in Fig. 11, but if there 
is applied a lesser amount of power each time and finally 
stopped, the amount of swing would gradually decrease 
and then completely die out. As shown in Fig. 12, the 
damped wave has a lesser amount of power behind each 
of the oscillations and in time the oscillations gradually 
die out where the continuous wave or un-damped wave 
keeps its momentum by having an even amount of force 
behind it on each oscillation. In damped waves there is 
a series of wave trains, as shown in Fig. 13. Comparison 
may be made of a damped wave from a spark station and 
an undamped wave from a C. W. or continuous wave sta¬ 
tion, to the difference between noise and music. Accord¬ 
ing to the teachings of Physics, music has a continuous 
wave, where anything rated as noise is made up of waves 
which have a difference in frequency or vibration. The 
noise which we hear after a thunder-clap, for instance, is 
very irregular while the music which we receive from a 


32 


RADIO THEORY SIMPLIFIED 


piano has a regular vibration to it. This might be carried 
a little farther, saying that there is as much difference 
between a spark and a C. W. station as there is between 
noise and music. A! 1 stations sending out dots and 
dashes are not using damped waves, but they can be 
distinguished. Many Ships and Government stations 



are using spark. Most of these, sooner or later, will be 
changed over The disagreeable features of the spark 
station will eliminate it in time, but until that time there 
will always be noises in the air. When using a receiving 
set one sometimes hears irregular waves which are caused 
by a street car going by the house, an arc light flickering 
in the vicinity and many other electrical disturbances 
which are sending out a non-continuous wave. It is 
nearly impossible to tune out or eliminate these waves, 
so when they are heard the blame should not be laid to 
the amateur who is thought to have a spark set. Now if 
the amplitude or height of a damped wave cannot be con¬ 
trolled, it cannot be used to transmit music and voice or 
be made into what is called a modulated wave. Hence it 
cannot be used for a radio telephone, but only in wireless 
telegraphy. As this book deals mostly with radio tele¬ 
phony, the theory of damped waves will be omitted and 
further explanations of C. W. will be considered. 




RADIO THEORY SIMPLIFIED 


33 


9. TRANSMITTING STATIONS: In transmitting 
stations that are used for radio telephony there is what is 
known as the oscillator. This is the generator of the radio 
frequency wave and this wave is used to transmit sound. 
In Chapter Three where an explanation of audion bulbs 
is given, space will be devoted to an explanation of how 
the bulb works as an oscillator. In radio code work 
there is also used a mechanical oscillator, but as an os¬ 
cillator of this type is not used for the transmission of 
sound, no explanation of this will be given. 




Fig, j4—Transmission and Reception of Continuous Radio Waves. 


By referring to Fig. 14 it will be noted that there is at 
the start, a sound wave impressed on a microphone. This 
is similar to an ordinary land line telephone. This sets 
up a pulsating or undulatory direct current. Then it, in 
turn, goes to the modulator where it molds or changes 
the amplitude of the radio frequency wave and this wave 


















34 


RADIO THEORY SIMPLIFIED 


is transferred to the aerial where it is in turn radiated in 
all directions. As this wave travels away from the trans¬ 
mitting station, it becomes weaker and weaker until it is 
so faint that the receiving instruments are not delicate 
enough to be affected by it. With the higher powered 
stations there is sufficient power whereby it may be 
received over a distance of many thousands of miles. 
There seems to be great confusion in the mind of a begin¬ 
ner in radio on what the range of any given broadcasting 
station is. Many times he is confused by thinking that 
the wave lengths in meters tell the range of a station. It 
is quite true that with the longer wave lengths it is easier 
to transmit great distances,. but this is because it is pos¬ 
sible with an apparatus which generates a long wave to 
put more power behind this wave. So the distance that 
a station can be heard depends on many things besides 
the length of the waves. One often hears the Radio Man 
speak of having a transmitting station which gives him 
so many amperes of radiation, or of a station which is 
of 5, 10, or 500 watts. To make this understandable one 
needs only to think of the average electric light using an 
alternating current. It is known that the brighter or 
stronger this light is, the greater the distance it will 
radiate its beams; also the rated voltage of the light 
makes no difference upon its brightness. The alternating 
current of electricity used in the average home is 60 
cycles and 110 volts and will work equally well on the 
5-watt lamp or on a 100-watt lamp; thus the same holds 
true in the use of radio. Within certain limits, a 5-watt 
station and a 500-watt station will work equally well on 
a 400-meter wave length, but of course the 500-watt sta¬ 
tion will carry farther, everything else being equal. Many 
times other things are not equal. 

Referring again to the distance which the light from 
an electric bulb would carry. A large electric light could 
be put in the center of a number of buildings or in a grove 
of trees and its rays would not carry as far as it would if 


RADIO THEORY SIMPLIFIED 


$S 

it were in the clear; so oftentimes we hear of a small sta¬ 
tion with small power getting out much farther than one 
of the larger stations. Much depends on how the station 
is kept up, how well the antenna is insulated and a good 
many other things, just the same as light waves will not 
radiate well from a bulb which is enclosed in a dirty glass 
shade. An operator of a broadcasting station cannot 
always tell how good his station is working and how far 
it is reaching. That is one of the reasons that it is desir¬ 
able to hear from the person who picks up broadcasting 
at a great distance away from his station. By having 
this information a check can be made upon the broad¬ 
casting station and thereby maintain it at its maximum 
efficiency. This is one of the reasons why we should 
always co-operate with station operators when they ask 
for cards from listeners-in. 

If the reader wishes to go more fully into the subject 
of the transmitting station, there are many good books 
upon the subject. The remainder of the space will be 
devoted to the explanation of how these radio waves are 
picked up and in fact how the different Receiving Sets 
work. These are the sets which the listener-in will op¬ 
erate and the better they are understood, the more pro¬ 
ficient he will become in operating them. 


^0 RADIO THEORY SIMPLIFIED 



Fi$. 15—Transmission and Reception of Radio Waves. 












CHAPTER II 


TRANSMITTING AND RECEIVING 
AERIALS 

10. USE OF THE AERIAL: In the past chapter it 
was shown how the modulated radio wave traveled out in 
all directions from the broadcasting station and how these 
waves affected the receiving circuit. It was then shown 
how these waves were rectified into a pulsating direct 
current passing through the telephone receivers of a set 
and there being changed into a sound wave which was 
audible to the human ear. 



When transmitting radio signals, the aerial and ground 
act as a large condenser which is charged and discharged. 
Sometimes instead of using the ground as one side of the 
condenser, a counterpoise is used. The counterpoise con¬ 
sists of a number of wires placed between the aerial and 
ground. 

To understand this, think of the ideal antenna. This 
would consist of two large plates of metal placed some 


37 













38 


RADIO THEORY SIMPLIFIED 


distance apart, forming in this manner a gigantic con¬ 
denser, being similar to any two plates of an ordinary 
small condenser. 

Fig. 16 is a diagram of an aerial such as we would have 
by using two metal plates. 

In order that the plates may have the merits of a good 
aerial they would have to be very large; so they are im¬ 
practical and in place of them different types of wire 



aerials are used which are less expensive, easier to install, 
and give good results. 

Fig. 17 shows a transmitting aerial of the flat top type, 
using the ground as the lower plate of the condenser and 
in Fig. 18 the same type of flat top is shown having a wire 
counterpoise instead of the ground to form one side of 
the condenser. 

Now as the station is transmitting, the aerial condenser 
becomes charged and discharged and this sets up a wave 
in the Ether which travels out in all directions. To receive 
these radio waves properly, another condenser or aerial, 








RADIO THEORY SIMPLIFIED 


39 


similar to the one used for transmitting, will be necessary, 
but as we do not have to handle the large amount of cur¬ 
rent which is necessary in a transmitting aerial, it can be 
of a much simpler design. The receiving aerial may be 
one of many different types. 

Ordinarily, one wire well insulated, which is kept away 
from all trees and buildings and is anywhere from 50 feet 
to 100 feet long and from 20 feet to 50 feet from the 
ground, gives good results for broadcast reception with 
most any type of set. 



Pig. 18—Antenna Using Counterpoise as One Side of Condenser. 


With the better type of sets which use one or more 
stages of radio frequency amplification, long distance 
reception can generally be had when using short or inside 
aerials. It must be remembered, however, that when 
using a short or inefficient aerial, the same signal strength 
will not be present in the aerial circuit and this must be 
made up by having a well designed and well built receiv¬ 
ing set. 















40 


RADIO THEORY SIMPLIFIED 


Fig. 19 shows a poorly constructed aerial, having a 
house, trees, and other obstructions close to the aerial 
wire and so cutting down its efficiency. It would have 
been much better to have placed this aerial in some other 
direction so that there would not be a decrease in the 
capacity effect by having objects of this kind between 
aerial and ground. 

11. LOOP AERIALS: In using a loop for reception, 
a somewhat different method is used and it can be com- 



Fig. 19—Inefficient Aerial haring Trees, Buildings, etc. in Condenser Field. 

pared more to that which is known as the inductance 
method of reception rather than the condenser method 
of reception. 

In using any type of inductively coupled set, we set up 
oscillations in the secondary coil which in turn go to the 


















RADIO THEORY SIMPLIFIED 


41 


detector, so with a loop or coil aerial the E.M.F. is set up 
in the loop or coil and goes to the first bulb. This type 
of aerial has a much less chance to pick up a strong incom¬ 
ing wave so. that the signal must generally be strength¬ 
ened before it can be detected in order for it to be audible. 
For this reason, radio frequency amplification is generally 
used in connection with a loop especially to receive dis¬ 
tant stations. 

Further information regarding loop antennae is given 
in Chapter 5. 



Fiji. 20—Tuning the Antenna by Using Tapped Coil and Variable Condenser. 


With very sensitive sets the wire in the set is sometimes 
sufficient to pick up a signal, or sometimes the ground or 
aerial is used alone. When this happens, the same effect 
is present as with the loop. 

12. TUNING THE ANTENNA: When it is wished 
to tune a radio receiving set to resonance with the sending 






























42 


RADIO THEORY SIMPLIFIED 


station it is necessary to use some type of tuning appara¬ 
tus. This can be accomplished either by capacity tuning 
or by changing the inductance of the coils. Before these 
different methods are applied to the tuning of a receiving 
set, a short explanation of the different ways of doing this 



Fife. 21—Method of Usiufe Tapped Coll between Aerial and Ground. 


will be given. In Fig. 20 is shown a sending station which 
has an aerial condenser combined with the set that sends 
out a wave of 400 meters or 750 kilocycles. In the re¬ 
ceiving aerial condenser, there is a natural capacity which 
will receive a wave of say 150 meters in length or 2000 
kilocycles. The difference to be made up in the receiving 
set by some method of tuning would be 250 meters. One 
method of doing this would be to shunt a variable con¬ 
denser between the aerial and ground. This is shown by 














RADIO THEORY SIMPLIFIED 


43 


the dotted lines placed between the aerial and ground in 
Fig. 20. The second method that could be used would be 
to make up for the lack of wire in the aerial and ground 
lead by placing some kind of coil, with a number of turns 
of insulated wire wound on same, between the aerial and 
ground. These coils are generally made up so that the 
number of turns can be varied. 




Fig. 22—Method of Using Variable Condensers to Tune Fixed Coils. 


The two different methods are shown in Fig. 2i. At 
‘‘A” there is an illustration of a two slide tuning coil with 
an aerial fastened to one slider rod and the ground to the 
other. At “B M there is a tapped coil such as is used on a 
vario-coupler. 

It can readily be seen that with either of these methods 
of adjustment and with a coil sufficiently large so that 
enough turns may be put into the circuit, the aerial can 
be tuned in resonance with transmitting stations sending 
out waves of different lengths. 

















44 


RADIO THEORY SIMPLIFIED 


Oftentimes a combination of condenser and inductance 
is used. In Fig. 22 at “A” the variable condenser is 
shunted across the coil and at “B” it is in series with the 
coil. A good thing to remember is that shunting a coil 
with the condenser raises the natural wave length of the 
tuning device and putting it in series with either the aerial 
or ground, lowers the natural wave length of the tuning 
devices. 

Often coils used for tuning purposes have no way of 
varying the number of turns. The most common of these 
are the spider web and honeycomb coils. When these are 
used, a condenser is generally shunted across or connected 
in series with the coil. With this type of coil, dead end 
losses are eliminated, due to having all of the wire in the 
circuit at all times. 

Another method of tuning is by having two separate 
windings connected in series. Changing the positions of 
these windings will then change the inductance of the 
tuning device. A variometer in the aerial circuit employs 
this method. 

When a receiving set uses both a primary and second¬ 
ary coil for tuning, the secondary circuit must also be 
tuned by the use of a tapped inductance, a variable con¬ 
denser, or by the introduction of a variometer in the 
secondary circuit. With many of the newer types of radio 
frequency amplifying sets, the aerial or primary circuit 
is not tuned. A sufficient number of turns is wound on a 
coil and this is closely coupled to a secondary tuning coil. 
Oscillations will then be set up in this secondary coil if 
same is brought in resonance with the radio wave which 
it is desired to hear. 


CHAPTER III 


THE OPERATION AND ACTION OF 
CRYSTAL DETECTORS AND 
AUDION BULBS 

13. RECTIFICATION OF RADIO FREQUENCY 
WAVES: In the past chapter was shown how the modu¬ 
lated radio waves travel out in all directions from the 
broadcasting station. In Fig. 14 was shown, how the 
aerial of the transmitting station sent out waves and how 
these waves affected the receiving circuit. It is then 
rectified into a pulsating direct current passing through 
the telephone of the receiving set and there being changed 
into a sound wave audible to the human ear. Fig. 15 also 
shows this wave action. 



Fift. 23—Crystal Detector Rectification of Radio Waves. 


There are many different types of receivers and in all of 
these, two main methods are used for rectification. The 
first to be described will be the crystal detector and the 
second the audion bulb. 


45 











46 


RADIO THEORY SIMPLIFIED 


14. CRYSTAL DETECTOR RECTIFIER: In Fig. 
23 is shown a common crystal detector circuit. The prop¬ 
erties of the crystal or mineral that is used are such that 
it will pass a positive current of electricity better than it 
will a negative current. In Galena this ratio is ten to one 
(10-1). That is, it will pass a positive charge of electricity 
ten times easier than it will a negative charge so that the 
negative charge is intercepted and will not pass the detec¬ 
tor to any considerable extent. This is the reason that 
only one half of the cycle is present in the circuit beyond 
the crystal detector and this wave can be shown as in Fig. 
23 at “A.” This pulsating direct current is then passed 
on to the telephone which will not vibrate to the numer¬ 
ous pulsations of the radio frequency wave and con¬ 
sequently we hear only the sound caused by the curve of 
the modulated wave. This is the same curve that would 
apply to the modulated radio frequency wave which was 
set up at the broadcasting station. This modulated wave 
actuates the diaphragms of the telephone receiver and 
causes a sound audible to the human ear, similar to the 
sound given at the microphone of the broadcasting station. 

Since the telephone receivers will not respond to the 
pulsation of the high frequency wave, most radio receiv¬ 
ing sets have a by-pass condenser placed across the phone 
terminals to enable these high frequency waves to pass 
around the high resistance of the coils in the receivers. 
There is, however, a small capacity effect between the 
two wires which run parallel in the cord connecting the 
receiver or loud speaker to the set and this capacity is 
sometimes great enough so that a by-pass condenser is 
unnecessary. 

15. THE AUDION BULB: The second method used 
for the rectification of radio waves is with an audion bulb 
or vacuum tube. These are sometimes also called ther- 
monic valves. A whole volume could be devoted to a 
most complete explanation of this wonderful invention 
but as space does not permit, a short understandable 


RADIO THEORY SIMPLIFIED 


47 


outline of the tubes as used for broadcasting transmission 
and reception will be all that is given in this book. To 
thoroughly understand the action of an audion bulb one 
must have a slight understanding of the electron theory. 

16. THE ELECTRON THEORY: Heretofore it 
has been stated that volumes could be written about the 
audion bulb. The same holds true for the electron theory 
and in fact, Prof. Millikan (who has claimed to have 
isolated and weighed the electron) has written a volume 
dealing with practically nothing but this subject.* The 
electron is the smallest particle of matter to have been 
thus isolated and weighed and although it would take 
many millions of these to make a particle of matter large 
enough to be seen, the basis of Prof. Millikan’s mathe¬ 
matical calculations seems to be sound and his theories 
are generally accepted as being true. 

An electron is a negative charge of electricity which, 
except in an extremely cold temperature, is in constant 
motion. As the temperature rises, these electrons become 
more active until they reach such a high boiling point that 
they are thrown out into space. This is the reason that 
an electron discharge is present around the heated fila¬ 
ment of an ordinary electric light bulb as well as in the 
audion bulb w r hich is used for radio work. When a body 
has too many of these electrons, it is said to be negatively 
charged and when it is lacking in electrons it is thought of 
as having a positive charge. The electrons are a nega¬ 
tively charged body and will always be attracted by any 
other body which is lacking in electrons. 

Certain substances offer an easier path for the flow of 
electrons than others. This is the reason for wires of a 
high resistance and wires of low resistance. When the 
construction of a wire is such that the resistance to the 
flow of electrons through the wire is not great, it can be 
said that the wire is of low resistance. If the substance 


*The Electron, its Isolation and Measurement—The University of Chicago Press. 



48 


RADIO THEORY SIMPLIFIED 


of the wire is such that it hinders the flow of electrons 
through the wire, it is known as having a high resistance. 
The reason that some substances have this high resistance 
is because the composition of the atoms (the atom is com¬ 
posed of both positive and negative charges of electricity) 
is so dense and closely packed as to make it difficult for 
the negative electrons to flow and if a great many elec¬ 
trons are forced through them they will heat up in passing 
an electric current. This varies greatly with the different 
substances. With glass, porcelain and other high di- 



Flg. 24—Electron Flow between Filament and Plate. 

electric composition, the resistance to the flow of the 
electrons is so high that they are used for insulation 
between electrically charged bodies. Much more could 
be said about the electrons but for the purpose of this 
book, suffice it to know that electrons are emitted from 
the heated filament of an electric bulb and that these 
electrons will be attracted by any body which is positively 
charged or lacking in electrons and that these electrons 
will travel through a partial state of vacuum better than 
through air of ordinary density. 









RADIO THEORY SIMPLIFIED 


49 


17. TWO ELEMENT BULB: Consider now the 
action of this electron flow between the filament and plate 
of a two-element bulb. Fig. 24 shows a drawing of a two- 
element bulb connected to an “A” and “B” battery and 
using a milliammeter in the plate circuit. When the fila¬ 
ment of the tube is heated by the ‘‘A” battery, electrons 



are present around this filament. These electrons will be 
attracted by anything which is positively charged. The 
plate or second element in the tube can then be connected 
to the positive side of a “B” battery and this will put a 
positive potential or charge on the plate in the tube. This 
















50 


RADIO THEORY SIMPLIFIED 


positively charged plate will then attract the negative 
electrons which are being emitted from the heated fila¬ 
ment. This electron flow can be controlled by changing 
the temperature of the filament with the rheostat, which 
is in series with the “A” battery. By inserting a milli- 
ammeter in the plate circuit, the current present can be 
measured. The two-element tube can be used as a recti¬ 
fier of alternating current and is so used in some trans¬ 
mitting stations. It can also be used as a rectifier of the 
high frequency radio waves and was used in this man¬ 
ner in radio work before the introduction of the three-ele¬ 
ment tube such as used today. Fig. 25 shows the hook-up 
using the two-element tube. 


jSsaaMsg i&ivc 



Flu. 26—Water Analogy Showing Use of Grid. 


18. THREE ELEMENT BULB: Consider next the 
operation of the third element which is added to an au- 
dion bulb. It has been shown that there was an electron 
flow between the heated filament and the plate. The two- 
element bulb was invented by Fleming and has been in 
use since 1904. In 1907 the three-element bulb was in¬ 
vented by Dr. Lee DeForest. This perfection of the Flem¬ 
ing valve has been one of the outstanding steps in radio 













RADIO THEORY SIMPLIFIED 


51 


advancement and it is due strictly to the field opened up 
by this invention, that it is now possible to transmit 
sound by radio. All of the wonderful features of broad¬ 
casting today owe their existence to this perfection of the 
Fleming valve. To explain the sensitiveness of an audion 
bulb using the three elements, a water analogy is made 
use of. 




In Fig. 2, Chapter I, was shown how water flowing 
through a pipe could be used to explain the resistance 
that was set up in a wire when passing an electric current 
through same. A similar type of drawing can be used to 
show the action and use of the grid in a vacuum tube, 
how this grid can control the electron flow between the 

























52 


RADIO THEORY SIMPLIFIED 


filament and the plate, and how it will take but a very 
weak signal to actuate this control. In Fig. 26 is shown 
a water pipe filled with water and a water pump which 
keeps a 20-pound pressure on a part of the pipe. Inserted 
in this pipe is also a valve which will control the flow of 
water between stations “A” and “B”. As one knows, it 
will take very little power to either open or close the valve 
at “C” and that this small amount of power will control 
the greater power which is being used to force the water 



Fig. 28 —Action of Three Element Bulb when Grid is Negative. 


through the pipe. The same holds true with an audion 
bulb. The electron flow or power used to actuate the 
telephone receivers is furnished by the batteries. The 
“A” battery heats up the filament of the bulb and starts 



































RADIO THEORY SIMPLIFIED 


53 


the electron flow between the filament and plate while 
the grid acts as a valve to either retard or help this elec¬ 
tron flow. In the three-element tube the grid lies between 
the filament and plate and is generally made of some fine 


MOOUUT7co 



Fig. 29—Modulated Radio Wave Train. 


wire mesh or screen which will facilitate the flow of elec¬ 
trons between filament and plate. The incoming wave is 
an alternating current; first positive, then negative. 
Sometimes it is strong and sometimes it is weak. When 
it is strong it is said to have a high amplitude and when it 
is weak it is said to have a low amplitude. When the in¬ 
coming wave is positive, the grid will also be positively 
charged and will help the flow of electrons from the fil¬ 
ament to the plate. When the incoming wave is negative, 
the grid will be negative and this will retard the flow of 
electrons between filament and plate. Fig. 27 shows the 




































54 


RADIO THEORY SIMPLIFIED 


action of the bulb when the incoming wave is positive and 
Fig. 28 shows the action when the incoming wave is 
negative. 

This increase or decrease of the flow of electrons is the 
cause for the variations of the pulsating direct current, 
present in the telephone circuit. The grid changes in 
polarity or goes from positive to negative, many thou¬ 
sands of times per second. The diaphragms of the receiv¬ 
ers will not vibrate fast enough to register these pulsa¬ 
tions. There is also present w r hat is called a modulated 
wave which is a line drawn at the height of the amplitude 
of the radio frequency wave. This wave is shown in Fig. 
29 and is the one which will affect the telephone receiver. 

19. GRID CONDENSER AND LEAK: The be¬ 
ginner in radio hears much about the different types of 
grid condensers and leaks. There are many varieties of 
variable grid leaks on the market and w r here one is not 
furnished with a grid condenser, an additional piece of 
cardboard or other substance may be put across the ter¬ 
minals of the condenser while a pencil mark or mark made 
with India ink makes a suitable leak and can be easily 
varied. The following explanation tells why the leak 
must be varied for different kinds and types of tubes. 

The grid condenser is always connected in series with a 
tuning apparatus so that with the variations of the alter¬ 
nating current wave, the condenser becomes charged and 
discharged and likewise puts a positive and negative 
potential on the grid of the tube. Various detector tubes 
have different characteristics but with most of them, by 
using a grid condenser and leak, better reception is ob¬ 
tainable. 

Fig. 30 represents a drawing of a well modulated con¬ 
tinuous wave. The upper half of the wave is positive and 
the lower half negative. According to the previous ex¬ 
planation of the audion bulb, the filament throws off the 
negative charges of electricity which are attracted by the 


RADIO THEORY SIMPLIFIED 


55 


positively charged plate. Now as the grid becomes posi¬ 
tively and negatively charged, it helps or retards the flow 
of the electrons. 

When the incoming oscillations are positive, the grid is 
positive and consequently will pick up some of these neg¬ 
atively charged electrons the same as the plate, but when 
the incoming oscillations change to negative, it will not 
be able to get rid of all of the electrons which it has col¬ 
lected, so the grid still holds some of these electrons and 
each time the frequency changes it will add to the number 
of electrons on the grid. If there was no let-up in the 



storing up of this charge on the grid, they would soon 
become so numerous that they would hinder or stop the 
flow between the filament and the plate, so in most types 
of radio transmitting stations there is a means of breaking 
these continuous oscillations so that the grid will have a 
chance to become discharged. 



















































56 


RADIO THEORY SIMPLIFIED 


Refemng again to Fig. 30, there is a well modulated 
wave and at the point “A” it is near a zero point and from 
there to point “B” there is that which is known as a mod¬ 
ulated wave train. Now at these two points “A” and “B” 
the grid will have a chance to become discharged by hav¬ 
ing the negative charge of electrons leak off through the 
grid condenser and back into the “A” battery circuit. If 
a tube were used in which there was a perfect vacuum, it 
could only happen in one way, but in all commercial 
tubes there is some gas left in the tube and part of this 
charge leaks off through these gases and through the walls 
of the tube. The rest of the charge leaks back through 
the grid condenser. To be sure that this happens before 
the next wave train starts, a large resistance of from one 
to five megohms (a megohm is 1,000,000 ohms) is put 
across the condenser, which helps to relieve the grid of 
this charge. (This is a very important thing for the op¬ 
erator of a receiving set to remember.) 

As stated, some of this charge on the grid leaks off 
through the gases in the tubes and that which does not, 
must leak through the grid condenser and grid leak. All 
tubes are not alike and even two tubes of the same make 
may not have the air pumped out to the same state of 
vacuum, so that oftentimes to get the best results the 
grid leak must be varied to operate right with the par¬ 
ticular bulb in use. Too much of a grid leak is as bad as 
not enough. For this reason it is always advisable to have 
a variable grid leak or some method of changing this leak. 

20. AUDIO FREQUENCY AMPLIFICATION: It 
has been explained how the audion bulb acts as a rectifier 
and amplifier of the incoming alternating current radio 
frequency wave. So a similar type of bulb will act as an 
amplifier of the rectified wave after it leaves the detector. 
In fact, the audion bulb will work as an amplifier of any 
sound carrying electrical wave. 11 is so used by telephone 
companies on their long distance lines. 


RADIO THEORY SIMPLIFIED 


57 


They are also used in connection with speech ampli¬ 
fiers at many large gatherings. When used as an ampli¬ 
fier of audio frequency current in a receiving set the pri¬ 
mary of the transformer is connected where the phones 
would be used if it was not wished to use more than one 
bulb. This transformer changes the voltage of the pul¬ 
sating direct current. It also forms a means of coupling 
the two bulbs together without impressing the “B” bat¬ 
tery voltage which was in the plate circuit of the previous 
bulb. The two coils of the transformer will not pass this 
low voltage current but as the coils of the transformers 
are always closely coupled they will pass the sound carry¬ 



ing electrical waves which it is wished to amplify. The 
principle of this amplification can be very easily under¬ 
stood if the original explanation of the audion bulb is at 
all clear. A sound carrying wave is impressed on the grid 
of the amplifier bulb in the same manner that the carrier 
wave from the broadcasting station is impressed on the 


























58 


RADIO THEORY SIMPLIFIED 


grid of the detector bulb. This audio frequency wave 
which is present in the plate circuit of the detector bulb is 
then amplified many times by the electron flow across the 
tube of the second bulb. Since this tube does not have to 
be used for the rectification of this wave, a tube of a 
higher state of vacuum and higher voltage can be used. 
Hence, a greater amplifying effect is present than could 
be had from the detector tube. ' 




C~Bn77- 



Fiji. 32—Circuit Showing Resistance Coupled Audio- 
Frequency Amplifier. 


There are several ways of coupling tubes together in 
order to get this amplifying effect. Fig. 31 shows the 
hook-up generally used when using an iron core trans¬ 
former. Fig. 32 shows the hook-up using a “C” battery 
and high resistance in place of a transformer. This type 
of hook-up is not in general use. A “C” battery is some¬ 
times used in the grid circuit of the amplifier bulbs when 





























RADIO THEORY SIMPLIFIED 


59 


using a hook-up similar to the one shown in Fig. 31. 
Further explanation of this is given in the chapter de¬ 
voted to the different parts used in making up a radio set. 

21. AUDION BULB USED FOR AMPLIFICATION 
OF RADIO FREQUENCY WAVES: When using an 
audion bulb as an amplifier of the radio frequency waves, 
very weak signals can be strengthened and then be passed 
on to either a crystal detector or an audion bulb detector 
and changed into a rectified audio frequency current. 
When using a bulb in this manner it is not desired to have 



Fig. 33—Circuit Showing Transformer Coupled Radio 
Frequency Amplifier. 


the radio frequency bulb act as a rectifier of the incoming 
alternating current wave. This is done by keeping the 
grid voltage Of a value that will not change the similarity 
of the operations in the plate circuit. In this manner the 
strength of the signal in each added stage of audio fre¬ 
quency amplification will be strengthened but will not in 
any way change, its form. Fig. 33 shows a schematic 
drawing of two stages of radio frequency amplification and 
Fig. 33A shows the amplifying effect of each one of these 




























60 


RADIO THEORY SIMPLIFIED 


stages although the proportion of amplification would be 
much greater than is shown in this drawing. The drawing 
is given merely to show the effect of the radio frequency 
bulb. 

Now if radio frequency bulbs will act as an amplifier 
of the incoming weak wave, loop aerials can be used. 
Also, much greater distances can generally be had as any 
weak wave which is present in the aerial circuit can be 
brought up to sufficient strength so that it can be rectified 
by using a crystal detector or a detector bulb. For the 
same reason that a transformer was necessary in the 
coupling of one or more stages of audio frequency ampli¬ 
fication to the detector, it is necessary to use some method 
of connecting radio frequency bulbs. This is generally 
done by using an air core transformer rather than one 
with an iron core but there are on the market several 
types of radio frequency transformers which have a very 
light iron core. When one or more stages of radio fre¬ 
quency amplification are used, it is called cascade ampli¬ 
fication. Quite often, instead of using a transformer 
coupling between the different stages, resistances or con¬ 
densers are used. These are used more extensively in 
foreign countries than they are in the United States. 
They are very efficient on the higher wave lengths but 
do not give the best of results on anything bdow one 
thousand meters. 

21-A. AUDION BULB USED AS A GENERATOR 
OF HIGH FREQUENCY CURRENTS: A better un¬ 
derstanding can be had of an audion bulb as a generator 
of high frequency currents after reading paragraph 23 
which takes up the theory of regeneration and paragraph 
24 which tells of re-radiation of regenerative sets. 

In some transmitting stations, audion bulbs are used 
to generate high frequency currents. These currents are 
used for the transmission of radio signals. Any regener¬ 
ative circuit such as shown in the next chapter, can be 


RADIO THEORY SIMPLIFIED 


61 


made to generate spontaneous oscillations. This is 
brought about in the following manner: every change in 
the grid voltage causes a greater change in the plate cur¬ 
rent. In order to make the tube oscillate it is then only 
necessary to have some method of coupling the plate cir¬ 
cuit to the grid so that the greater current in the plate 
circuit will supply a small amount of power to the grid 
and make possible a surplus power which is available for 
use in an external circuit. 

This surplus power can be sent into an antenna in the 
form of continuous or undamped oscillations at a fre¬ 
quency it is desired to use. 



Fig. 33A—Effect of Radio Frequency Amplification. 













CHAPTER IV 

RECEIVING SETS 

22. FACTS ABOUT RECEIVING SETS: This 
chapter will be devoted to an explanation of the theory 
of the most commonly used types of radio sets. There are 
so many different types and kinds of receiving sets and 
hook-ups on the market that it is confusing to the begin¬ 
ner in radio to know which one of these will be best for 
him to buy or build. 

The author has been asked hundreds of times which is 
the best set to build or buy and what the price of buying 
or building a good radio receiving set would be. The 
question has always been hard to answer as much depends 
upon the amount of money which the purchaser wishes 
to spend, just how much he expects to receive from the 
set and the condition under which the set must operate. 
Ordinarily a simple type of set will give better results 
when used in rural districts where there is not a great deal 
of congestion of electric wires, telephone wires, street car 
lines, large buildings, motors, etc. than it does in the city 
where this congestion does exist. 

The beginner who wishes to construct his own set 
should start out with one of the simple hook-ups and after 
he has become familiar and has learned to use and get the 
most out of his set, he will want more “miles per hour” or 
greater distance, “more riding comfort” or less inter¬ 
ference and the desire to always want something better, 
will stimulate his interest in radio the same as it did and 
does in the automobile. 

Many writers tell us to buy only high priced merchan¬ 
dise. This is not a rule which is always necessary to fol¬ 
low. Experience has shown that the beginner in radio 
could generally get as much actual satisfaction out of the 


62 


RADIO THEORY SIMPLIFIED 


63 


cheaper apparatus or out of the parts that he constructs 
himself, than he could from buying the best that could 
be had with the expectation of wonderful results. 

Many people started by driving one of the cheaper 
makes of car, and it would have been a mistake to have 
started in driving a high priced car. To begin with, if 
they ran it into the first telegraph pole they came to, it 
did’nt cost them so much and in the second place when 
anything went wrong (which always did sooner or later) 
they could fix it themselves or get some one who knew 
how to fix it. 

The same applies to radio apparatus. The man who 
wound his vario-coupler on an oatmeal can used a wood 
block for a rotor, baling wire to fasten it together, got 
more of a thrill out of hearing a station two hundred miles 
distant than a man who spent four or five hundred dollars 
for a set and heard stations across the continent. 

This is not an excuse for the manufacturer who turned 
out junk and oftentimes charged as much for it as is 
charged for good merchandise. Also, it should be un¬ 
necessary to pay a dollar and a half or two dollars for 
some simple little item that should sell for twenty-five 
cents or can be made by the experimenter with five cents 
worth of material. 

Many times the advanced radio man calls the simple 
types of receiving sets “Simple sets for simple people.” 
The same might be said of the Ford car, but to use the old 
advertised slogan “Go out on the street and watch them 
go by.” Quite true of the simple types of sets, you cannot 
tune out interference the same as could be done with a 
more expensive receiver, but it is also true that if you do 
not know how to operate a selective type of set, results 
obtained will be unsatisfactory. 

The drawing and explanation given will not give con¬ 
struction details. Directions in building different types 
of radio sets are given in another book written by the 


64 


RADIO THEORY SIMPLIFIED 


same author.* The diagrams and explanations here, are 
merely for the purpose of giving an idea of the theory and 
principle of different sets. 

23. THEORY OF REGENERATION: Before tak¬ 
ing up different types of receiving sets individually the 
theory of regeneration will be explained. The regener¬ 
ative principle will apply to several different sets which 
are explained later in the chapter. The regenerative idea 



originated with Armstrong a number of years ago and 
was perfected by him while a student at Columbia Uni¬ 
versity. A patent was applied for and entered in the Pat¬ 
ent Office in 1913. This patent was allowed and will not 


* “Radio Const ruction for the Amateur." 


















RADIO THEORY SIMPLIFIED 


65 


expire until 1930. The patent is now controlled by the 
Westinghouse Electric & Mfg. Company. Many suits 
have been started to break the patent but Armstrong’s 
title has always been upheld and he has always been 
declared the true inventor. 

Tuned plate amplification and feed back amplification 
are generally classified under two different headings: 
Altho the effect of these or results obtained are practically 
the same. The operation of this method of regeneration 
is somewhat as follows; the incoming radio frequency 
oscillations are repeated in the plate circuit and if coil is 
inserted in this circuit and can be tuned, it either assists 
or opposes the flow of current in the plate circuit, accord¬ 
ing to whether this current decreases or increases. There 
is a certain internal or s^elf capacity effect between the 
filament and plate of the audion bulb. The tuning of the 
plate circuit would have the effect of changing the space 
or capacity effect between the filament and plate accord¬ 
ing to whether or not the current was being helped or 
opposed. 

Where the single circuit regenerative and three circuit 
regenerative sets are dealt with separately the difference 
between tuned plate and feed back amplification will be 
explained. 

24. RE-RADIATION OF REGENERATIVE SETS 
A great deal is said and printed about the re-radiation of 
regenerative receivers. Interference caused by re-radia¬ 
tion is especially noticeable in the cities and towns where 
there are a number of regenerative receiving sets located 
within a short distance of each other. Much of the fading 
and the noise which are thought to be static are caused by 
the operator of a receiving set who is keeping the bulb in 
his regenerative receiver in an oscillating condition, thus 
causing interference. 

There are numerous receiving sets which use some 
system of radio frequency amplification. These do not 


66 


RADIO THEORY SIMPLIFIED 


cause a great deal of interference and, for the person who 
is constantly changing or experimenting with different 
hook-ups, we see no good reason why he should not use a 
set of this type. 

To the users of regenerative sets who have spent a great 
deal of money installing their receivers and who do not 
wish to spend the time or money to build or buy addition¬ 
al equipment, the following are general rules and instruc¬ 
tions which, if closely adhered to, will keep a regenerative 
receiver from interfering with reception by their neigh¬ 
bors. 

A regenerative receiver does not re-radiate except when 
the detector bulb is in an oscillating condition. When 
the bulb is oscillating, reception is not clear and before it 
can be cleared up, the bulb must be brought down below 
the oscillating point. This can be done in numerous ways 
with the different types of receivers. With the ordinary 
three circuit receiver, if the bulb is tuned down low and 
the tickler adjustment loosely coupled, the set will not 
re-radiate. One reason that the operator turns his bulbs 
on full is to enable him to hear the carrier wave from the 
different stations which he is trying to pick up. With 
almost any type of receiving set this is unnecessary and 
if the operator will get the bulb set at the proper point, 
get the coupling of his tickler coil at the proper place, and 
then tune with the balance of his tuning controls, he will 
find that he can pick up distant stations without causing 
interference with other receiving sets. 

As there are many different types of regenerative re¬ 
ceivers it is difficult to give detailed instructions on just 
how to keep all of them from oscillating; but, one thing 
to remember is that when your set is squealing or howling, 
this same sound is heard in all receiving sets which are in 
operation in your immediate vicinity. 

Drivers of automobiles are oftentimes told that “Cour¬ 
tesy will prevent accidents.” Courtesy in the air will also 
prevent interference with your neighbor and when op- 


RADIO THEORY SIMPLIFIED 


67 


erating a set a good thing to remember is “To do unto 
others as you would have others do unto you.” 

25. SINGLE COIL CRYSTAL SET: One of the 
simplest types of receiving sets is the single coil crystal 
set. Explanation of the operation of a crystal detector 
^e was explained in the last chapter. It was shown how the 
crystal works as a rectifier of the incoming alternating 
current wave. In previous chapters it was also shown 
how some type of tuning device must be provided to make 
up for lack of wire in the aerial and ground leads. 



With crystal detector sets all sorts of tuning devices 
are found. The simplest and most commonly used types 
are the two slide tuner and a single coil of insulated wire 
which is tapped, and can be varied by using a switch arm 
and contact points connected to the various taps. In Fig. 
35 is shown how a radio wave travels theoretically and 
how the aerial and ground, acting as a condenser, picks 
up this wave. The coil tunes the set to the proper fre¬ 
quency, the crystal detector turns the alternating wave 









68 


RADIO THEORY SIMPLIFIED 


into a direct current pulsating wave, and the modulated 
wave, which is made up by changing the amplitude of the 
carrier wave, actuates the telephone receiver, which in 
turn produces a sound audible to the human ear. In Fig. 
36 is shown a schematic drawing of this same type of 
crystal detector set. If the beginner is at all confused in 
reading schematic drawings, it will be best for him to 
study this simple type of drawing and compare it to the 
drawing in Fig. 35. In the next chapter symbols are also 
shown in connection with pictures of various radio parts 
used in making up receiving sets, and reference can also 
be made to these. 



Fig. 36—Crystal Detector Circuit. 


26. TWO COIL CRYSTAL SET: The two coil 
crystal set is similar in operation to the single coil crystal 
set explained in the previous paragraph. The difference 
is that a second winding is introduced. The primary or 
first winding is placed between the aerial and ground, and 
when tuned in resonance with the incoming wave and the 
secondary winding is tuned in a like manner, oscillations 
will be present in the secondary winding the same as 
though only one coil were used. The advantage to be had 
with a two circuit crystal set is sharpness of tuning or 
selectivity. 

Some method is generally provided for tuning both 
coils. When using a loose coupler for a two circuit crystal 
set, the primary or outside coil is generally tuned by the 







RADIO THEORY SIMPLIFIED 


69 


use of a slider connected to the aerial or ground lead and 
the secondary or inside coil is tuned by being tapped or 
by being shunted by a variable condenser. 

When using spider web or honeycomb coils, variable 
condensers are generally shunted across or put in series 
with either one of the two coils. In Fig. 37 two drawings 
are shown. The, one set at '‘A” is a drawing that would 
be used for twb,crystal set using a loose coupler and the 
one at “B" would be used in building a set using honey¬ 
comb or spider web coils. 



In all crystal detector sets there are only three major 
units; the tuning device, the crystal detector and the 
phones. The coil tunes the set to the wave, the crystal 
detector changes the alternating current wave to a direct 
current pulsating wave and the modulated wave which is 
made by changing the amplitude of the carrier wave 
actuates the receivers, thus producing sound. 

27. SINGLE CIRCUIT NON-REGENERATIVE 
SET: The single circuit non-regenerative set works sim¬ 
ilar to the crystal detector set only that instead of using a 
crystal detector to rectify the electric current oscillations, 
an audion bulb is used. Compare the drawing in Fig. 38 
to the Crystal drawing in Fig. 36 and it can be seen that 
they are the same except that in Fig. 38 an audion bulb is 
included in place of the crystal. This type of set is not in 












70 


RADIO THEORY-SIMPLIFIED 


general use because by using different methods of feed 
back amplification the efficiency of the set can be in¬ 
creased without much additional expense. The audion 
bulb is, however, a much better detector and a set using a 
bulb as a detector will have a greater range than one 
using a crystal. 



28. TWO CIRCUIT NON-REGENERATIVE SET: 
The two circuit non-regenerative set uses two coils for 
tuning the set in resonance to the incoming wave. The 
first or primary coil is composed of the wire between the 
aerial and ground and the second or secondary coil is 
placed close to the primary and when tuned in resonance 
with the primary an E.M.F. or electromotive force will be 
set up in this coil similar to the one present in the pri¬ 
mary. The two circuit receiver can be made from many 
diherent types of apparatus. When a loose coupler is 
used, the outside coil or primary is tuned by either using 
a slider rod with a slider to vary the number of turns or 
by being tapped and the inductance changed by using a 
switch lever. Additional tuning may be had by placing 
a variable condenser in series or shunted across the coil. 
The secondary of the loose coupler is the tube which slides 

















RADIO THEORY SIMPLIFIED 


71 


in or out of the primary and must also be provided with a 
system of tuning. 

Another tuning device used for a two-circuit is a Vario- 
coupler, where the outside coil is the primary and the 
rotor is the secondary. As the rotor is a fixed inductance 
it is generally shunted by a condenser so that it can be 
tuned. 



Other coils that can be used are honeycomb or spider 
web coils. As these are not generally tapped, condensers 
must be used for tuning. Fig. 39 shows two drawings. 
“A” uses either a loose or vario-coupler and “B” either 
honeycomb or spider web coil. 

The two circuit non-regenerative set has very few ad¬ 
vantages over the single circuit non-regenerative type 
and today it is not used. It is very sensitive but does not 
have a great range especially when compared with any 
of the regenerative types of receivers. An explanation 
was given so as to make it easier to explain different re¬ 
generative sets. 

In order to familiarize the reader with the different 
symbols used in schematic drawings, explanation of a few 
symbols used will be given. The arrow which is shown 
attached to the aerial wire and close to the coil means 
that there should be some method of varying the number 
of turns of wire on the coil. The long arrow across the 























72 


RADIO THEORY SIMPLIFIED 



two coils means that the two coils should have some 
method of varying the relationship between each other. 
The arrow across the condenser means that the capacity 
should be capable of being changed by moving the plates 
of the condenser closer together or farther apart. 


Fig. 40—Theoretical Operation of Single Circuit Regenerative Set. 

29. SINGLE CIRCUIT REGENERATIVE SET: 
There are probably more single circuit regenerative sets 
in use today than any other one particular type of set. 
The method of wiring these and the apparatus used varies 
greatly, but the general principle of the operation of all of 
them is the same. This set consists of some type of tun* 
ing device fastened between the aerial and ground and 
the regenerative action is had by inserting a separate vari¬ 
able inductance in the plate circuit or by using another 
coil placed in close relation to the tuning unit for the feed 


















RADIO THEORY SIMPLIFIED 


73 


back effect. The set is very efficient for use with just one 
bulb but is not at all selective and a great deal of agitation 
has been started to do away with it due to its being one of 
the worst offenders or re-radiators in existence. 

This set will not re-radiate and interfere with the re¬ 
ception by other people unless the bulb is in an oscillating 
condition. If the tickler coil is kept quite a distance away 
from the tuning coil or loosely coupled, and the detector 
bulb is turned down fairly low, good reception can be had 
without the set sending out oscillations over the receiving 
antenna. 



Many types of tuning units are used for building up 
single circuit receivers. The most common is the vario 
coupler, where the outside of the coil is used as the tuning 
coil and the rotor as the tickler, which is connected in the 
plate circuit. 






























74 


RADIO THEORY SIMPLIFIED 


Three figures are given in connection with single circuit 
regenerative set. The first of these, Fig. 40 gives the 
theoretical idea of the feed back action. Fig. 41 gives the 
drawing of a single circuit regenerative set such as would 
be used with a vario-coupler and Fig. 42 shows the same 
hook-up only that instead of using vario-coupler, two 
spider web or honeycomb coils are used. 

Sometimes single circuit regenerative sets are built 
which have a direct wire running from the plate circuit to 
the aerial. This is known as the ultra audion circuit. 


S P/DCRVCB O/Z 
//or/cyccna co/l.-$ 



a.SATT 



Fig. 42—Two Coil Single Circuit Regenerative Hook-up. 

30. THREE CIRCUIT REGENERATIVE SET: 
The term three circuit regenerative receiver is generally 
applied to a receiving set which consists of primary cir¬ 
cuit, secondary circuit and tuned plate circuit. Primary 
and secondary windings can be of various types. The 


































RADIO THEORY SIMPLIFIED 


75 


outside winding of a vario-coupler is sometimes used and 
is generally tapped and tuned by varying the number of 
turns between the aerial and ground. Oftentimes a vari¬ 
able condenser is also placed in the aerial or ground lead 
to give a finer tuning arrangement. The rotor of the vario- 
coupler is used as the secondary and is generally tuned by 
shunting with a variable condenser or by using a vario¬ 
meter in series with the windings of the rotor and the grid. 
Sometimes both a variometer and a variable condenser 
are used. In the third or plate circuit some type of vari¬ 
able inductance such as a variometer is introduced. 


V&Rig COUPLER, 

JLOO&E COOf>t.Cn 



Another type of three circuit receiver which is often 
built is one using three honeycomb or three spider web 
coils in place of the vario coupler and variometer. One of 
the coils is placed between the aerial and ground and is 
tuned by shunting or placing a variable condenser in 
series with it, the second coil is used as the secondary and 
is tuned by shunting a variable condenser across the coil. 























76 


RADIO THEORY SIMPLIFIED 


A third coil is used as a tickler and the regenerative action 
is controlled by some method of coupling or varying the 
coil in its relation to the secondary coil. 

Three circuit receivers do not re-radiate as easily as the 
single circuit regenerative sets but they will re-radiate to 
some extent. The only way this could be entirely elimi¬ 
nated would be to put one or more stages of radio fre¬ 
quency amplification in front of the detector bulb. Several 
articles have been written regarding the feasibility of 


HOHEVCOMB on 



using radio frequency amplification with regenerative sets. 
In certain cases manufacturers have successfully made 
sets using this method, but for the ordinary amateur it 
is thought best to stick either to straight regeneration or 
to a tuned radio frequency set of the Neutrodyne type. 

Two drawings are given of the three circuit receiver— 
the first, Fig. 43 gives the hook-up when using a vario- 






























RADIO THEORY SIMPLIFIED 


77 


coupler or loose coupler and two variometers. The second 
Fig. 44 shows the receiver using three honeycomb or 
spider web coil. 

31. THE REINARTZ RECEIVER is a type of single 
regenerative set perfected by John L. Reinartz, a well 
known radio experimenter and operator. It was per¬ 
fected several years ago and is used extensively by the 
licensed transmitting operator for the reception of mes¬ 
sages on the shorter wave lengths. It is one of the sharpest 



and easiest of the regenerative sets to operate, therefore, 
it is an ideal receiver for the man who is handling traffic. 

The basis of the circuit is the Reinartz coil which is 
constructed with the antenna, grid and plate windings 
on the same form usually in some form of spider web coil. 
The efficiency of the set is due to the extremely close 

















78 


RADIO THEORY SIMPLIFIED 


coupling obtained between the circuits and the ease with 
which they may be controlled by the use of the tuning 
controls. Fig. 45 shows the old standard hook-up using 
tapped coils, but recent perfections have been made in 
the circuit whereby taps are eliminated and all tuning 
done by variable condensers. 

32. NEUTRODYNE SETS: One of the most pop¬ 
ular types of radio frequency sets being built and sold at 
the present time is the Neutrodyne on which U. S. Patent 
No. 1,450,080 has been issued. There have been many 
arguments regarding the efficiency of two stages of radio 
frequency amplification and detector as compared to a 
single circuit single tube regenerative set. Much can be 
said in favor of radio frequency amplification if it is 
properly controlled. 



Both tuned and untuned radio frequency amplifiers 
have been used for a number of years. Until just recently 
however, trouble was generally experienced in keeping 
the radio frequency bulbs from oscillating. Radio fre¬ 
quency amplification could be controlled better when 
receiving long waves than it could when receiving short 










































RADIO THEORY SIMPLIFIED 


79 


waves which are used in broadcast work. With the 
Neutrodyne Prof. Hazeltine devised a scheme for pre¬ 
venting oscillation of the radio frequency bulbs by the 
introduction of two small capacity condensers placed 
between the grids of the bulbs, and by the use of specially 
designed radio frequency transformers. 


57QGE S?.r 



The Neutrodyne consists of the following units—a 
tuning unit, which is generally the same as the two radio 
frequency transformers — the first stages of radio fre¬ 
quency amplification and the second stage of radio fre¬ 
quency amplification. The primaries of the tuning unit 
and transformers is untuned but the secondaries are tuned 
by shunting them with variable condensers of sufficient 
capacity to tune the coil over the desired band of wave 
lengths. 

There is this disadvantage in radio frequency ampli¬ 
fication—more tubes are used and as all of them will have 














so 


RADIO THEORY SIMPLIFIED 


to be working in a proper manner before reception is at 
all clear, this somewhat complicates the operation of the 
set. The fact that all of the units must be in syncronism 
before the station is heard makes the set extremely selec¬ 
tive and if a set of this type is properly constructed and 
operated, stations which are operating on almost the same 
wave length can be separated. Stations which are allotted 
the same frequency or wave length can be separated due 
to their not adhering strictly to their assigned frequency 
thus giving a variation of several meters which will allow 
the operator with a good set to tune either one of them in. 
Fig. 46 shows a schematic drawing of the five bulb Neu- 
trodyne using two stages of radio frequency amplification, 
detector and two stages of audio frequency amplification. 



33. REFLEX CIRCUITS: A short understandable 
explanation of the complete reflex action is very hard to 
give due to the fact that the theory of the circuit is ex¬ 
tremely complicated. A short understandable explana- 


C^ysr/7/. Q£? 








































RADIO THEORY SIMPLIFIED 


81 


tion will be given however, and it is believed will give the 
reader a fair understanding of the principles underlying 
the circuit. 

The reflex circuit has become very popular due to its 
having a duplex action which will give considerable dis¬ 
tance and good volume when using only a small number 
of tubes. In reflex circuits the amplifier bulbs are used 
for both radio and audio frequency amplification. Some¬ 
times a crystal detector is used for rectification and some¬ 
times an audio detector bulb is used for this purpose. 
Recently the two element peanut bulb has been incorpor¬ 
ated in this circuit as a detector. 

In all of the circuits when using one, two or three bulbs, 
the action is somewhat as that shown in Fig. 47. The 
incoming radio frequency wave is impressed upon the 
first bulb or the first stage of radio frequency amplifi¬ 
cation and then goes to the next stage of radio frequency 
amplification and then to the detector where it is recti¬ 
fied and passed back through the bulbs again for audio 
frequency amplification. Not more than three bulbs are 
generally used because the bulb in the last stage would 
become overloaded due to its having to carry the maxi¬ 
mum amplified current from both audio and radio fre¬ 
quency circuits. 

There are many ways of getting the Reflex Action and 
in some of these the first bulb is used for radio frequency 
amplification only while the second bulb furnishes the 
second stage of radio frequency amplification and one set 
of audio frequency amplification. 

Fig. 48 is the drawing of a two bulb reflex set. 

34. AUDIO FREQUENCY AMPLIFIERS: Often¬ 
times audio frequency amplifiers are built and sold in 
separate units. This type of amplifying unit can be used 
to amplify any type of sound carrying electrical wave and 
they also can be used with any type of radio receiving set. 


82 


RADIO THEORY SIMPLIFIED 


The theory of audio frequency amplification was ex¬ 
plained in the last chapter. Audio amplification can be 
accomplished by using either resistance or by the use of 
transformers. The type most commonly used is that 
using transformers for the coupling of the bulbs. These 
units do not generally consist of more than two stages, 
as the signals become distorted due to having tube noises, 
and to the fact that all outside interference is also ampli¬ 
fied along with the signal which is desired to be heard. 

Audio frequency amplifiers have been the same for 
many years and the connections which are being used 
today are the same as was used from the start. Trans¬ 
formers and other materials have changed but the hook¬ 
up has not. 

35. SUPER-HETERODYNE. The super hetero¬ 
dyne receiver is perhaps the highest type of receiver in 
general use today. While extreme care must be given to 
the design and construction of this set and the apparatus 
used to build it, the actual operation is comparatively 
simple. 

The super-heterodyne was conceived by Major Arm¬ 
strong soon after the introduction of his regenerative set. 
It comprises a method of changing the incoming radio 
frequency wave to one of lower frequency or longer wave 
length which can be very efficiently amplified by the use 
of different stages of radio frequency amplification—pro¬ 
cesses as follows—By the addition of another wave to the 
incoming radio frequency wave, a beat note of higher or 
lower frequency may be obtained. By so controlling the 
added wave, we can obtain a resultant which can be very 
efficiently amplified. 

In Figs. 49A and B schematic drawings of the Super- 
Heterodyne are given. A two circuit tuner is used with a 
detector connected in the usual way. The local oscillator is 
inductively coupled to the secondary of the tuner. This 


^orrccro^ 




g 

* 

J 

3 

s] 

1 

UMiL 


j^nnnnnnnnnnnnm 


FI*. 49A 

Condensed Drawing of Super-Heterodyne. 

NoUi Radio frequency amplifier unit fieaerally consists of three bulbs and audio frequency unit of two. 































84 


RADIO THEORY SIMPLIFIED 


local oscillator generates the interfering wave. The radio 
frequency amplifier is the conventional type excepting 
that it is designed to amplify at a high wave length. The 
second detector is necessary because the frequency at 
which the signal is amplified is still at a higher frequency 
than can be heard. In practice the R. F. amplifier usually 
consists of three stages. Two stages of audio are also 
usually employed. To increase the range of the set, in¬ 
crease the number of stages of R. F. However, eight is 
about the limit for practical operation. Hard tubes are 
used for both amplifiers and oscillators but soft tubes for 
detectors. 

36. THE ACMEDYNE CIRCUIT is one of the latest 
types of tuned radio frequency sets. Recently the name 
of this set has been changed to “Telemonic”. This 
change was made at the request of the Acme Transformer 
Company because of the similarity between this name 
and the name which is given to their transformers. The 
Acmedyne set is similar in operation to the Neutrodyne 
set explained in Par. 32 excepting that instead of using 
fixed inductances tuned by variable condensers for radio 
frequency transformers, a type of vario-transformers is 
used. The coils of these transformers are wound in the 
shape of a figure “D” and consist of a number of these 
windings wound on cardboard forms. This makes one of 
the most efficient types of variable transformers it is pos¬ 
sible to build. The losses are very low because they do 
not use variable condensers or have a great deal of metal 
or diaelectric in the electro-magnetic field. 

The set was developed by Lester L. Jones and complete 
units are being made by the Amsco Products Company, 
Inc. who use the trade name “Melco Supreme” and by 
other well known radio manufacturers. Parts to build 
the set are also available so that the fan who wishes to 
build his own set can do so. The set is neutralized by the 
use of compensating condensers mounted so that they 



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PH <-* 


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86 


RADIO THEORY SIMPLIFIED 


can be readily adjusted for any tubes which might be 
used. Similar to the Neutrodyne set, all of the controls 
must be set at the proper place and the vario-transf or Fri¬ 
ers and variometers must be working in synchronism 
before the set will operate successfully. Because of this, 
it makes a very selective receiver. 

Fig. 50 shows a schematic drawing of the set and also 
the outline of the windings for the vario-transformers. 
By studying this diagram, it will be noted that the set 
consists of three major tuning units. The first, a vario¬ 
meter which is constructed similar to the vario-trans- 
formers and the second and third; the vario transformers 
which are used in the radio frequency circuit. As the set 
gives a strong signal when only using two stages of radio 
frequency amplification and detector, one stage of audio 
frequency amplification is only used. For ordinary pur¬ 
poses this is found to give sufficient volume but when this 
set is used in halls or in the open, some type of power 
amplifier is generally added. One of the features of the 
ready built set is the use of a high resistance of 100 ohms 
to connect the “A” and “B” batteries together. In so 
doing it is nearly impossible to burn out the filaments of 
the tubes due to accidental crossing of some “B” battery 
wires with the filament leads. 

The set will work satisfactorily when using an outdoor 
or indoor aerial, loop or lighting plug. The set can also 
be calibrated, or the readings for the various stations can 
be logged and then be referred to when it is desired to 
pick up the same stations on different occasions. 

37. INVERSE DUPLEX: The inverse duplex cir¬ 
cuit has been developed in this country by David Grimes 
of New York City and was adapted from the French cir¬ 
cuit developed by an eminent French engineer, Latour. 
This set is similar to the reflex insomuch as the bulbs are 
used for both radio and audio frequency amplifications. 
The system of passing the current through is somewhat 



ujiJUimiLUJU/ 












































































































88 


RADIO THEORY SIMPLIFIED 


different. As stated in the past paragraphs one of the dis¬ 
advantages of the reflex circuit was that the last stage 
would become overloaded due to its having to carry the 
maximum load. With the inverse duplex set this dis¬ 
agreeable feature is overcome by passing the current 
through the first stages of radio frequency amplification, 
then using the last stage of radio frequency amplification 
for the first stage of audio frequency amplification, etc. 
Fig. 51 will explain this action. 


t*Srr>Gc R/toto rncpu^rtc y rtnr>K> rnco r 

vtkc fturxo 7 yr£.Quc»cv /'‘'since nuoto r/?gor oeicc.ron acM. 13 ^ 



Fig. 51 

Drawing Showing Inverse Duplex Action of Bulbs. 


The hook-up is being used very much for the construc¬ 
tion of portable sets. Tubes of the peanut type can be 
used and since a good volume and great distance can be 
had when using only three bulbs, the set will work very 
well for the experimenter who wishes to build a set in a 
compact form. If used in connection with a loop only 
one tuning control is necessary, being the variable con¬ 
denser which is shunted across the loop. Recently ex¬ 
perimental work has been conducted using tuned radio 













Fig. 52 

Three Bulb Grimes Inverse Duplex Circuit. 

































































90 


RADIO THEORY SIMPLIFIED 


frequency transformers in connection with an aerial. A 
set of this type gives extreme selectivity and great dis¬ 
tance, only it is very hard to operate and Vernier control 
is necessary for tuning. 

Fig. 52 gives a schematic drawing of a three bulb 
Grimes Inverse Duplex. 

38. RADIO FREQUENCY AMPLIFIERS (TRANS¬ 
FORMER COUPLED): Radio frequency amplifying 
units such as shown in Fig. 53 have been used by the 
Army and Navy of this and foreign countries for a num¬ 
ber of years. Sometimes as many as ten or more stages 
of radio frequency amplification were used, and for use 
on the higher wave lengths extremely high efficiency could 
be had when using only a loop for an aerial. As previously 
explained, the straight transformer coupled radio fre¬ 
quency set does not lend itself well to use on the broadcast 
wave lengths. This is caused by two reasons—first the 
radio frequency transformers are designed to give a maxi¬ 
mum efficiency on just one basic frequency and as broad¬ 
casting stations use quite a range of frequencies it would 
be very hard to make one of these transformers which 
would give maximum efficiency over the whole band of 
wave lengths. The theory of radio frequency amplifi¬ 
cation when using either tuned or untuned transformers 
was explained in the past chapters so no more will be said 
regarding this. 

Fig. 53 is that of a seven tube set using four stages of 
radio frequency amplification—detector and two stages 
of audio frequency amplification. 

39. RADIO FREQUENCY AMPLIFIERS(TUNED) 
The type of tuned radio frequency amplifier has been 
explained previously. Both the Neutrodyne and Acme- 
dyne circuits use this principle. One of the old time 
tuned radio frequency amplifying units is shown merely 
to give the reader an idea of the different steps through 


SsaaJRXSLXCSai. 




Fig. 53 

Un-tuned Transformer Coupled Radio and Audio Frequency Circuit. 
























































































































92 


RADIO THEORY SIMPLIFIED 


which development has been made. The set shown in 
Fig. 54 is that of a five bulb tuned radio frequency ampli¬ 
fier using transformers such as was used for this purpose 
before the introduction of the Neutrodyne and Acme- 
dyne sets. 

40. POWER AMPLIFIERS: When wishing to get 
a great deal of volume such as would be necessary in a 



large hall or when used in connection with large gather¬ 
ings outdoors, radio sets are built which incorporate one 
or more stages of power amplification. This is no 
more or less than audio frequency amplification, only 
that instead of using the common type of audio frequency 
amplifying bulbs, special bulbs are used in connection 
with specially designed transformers to give clarity with¬ 
out distortion. 











































RADIO THEORY SIMPLIFIED 


9S 


If more than two stages of straight audio frequency 
amplification were used the last bulb and transformer 
generally would become so overloaded as to make the 
signals very distorted. Several types of push pull trans¬ 
formers have been developed for power amplification. 
These transformers help to keep down the distortion due 
to having a balanced circuit which uses two bulbs in place 
of one. 


7°USH . 7KnNs> rORMElR'Sy 



Fig. 55—Two Bulb Push-pull Amplifying Unit. 


Fig. 55 shows a hook-up for a one stage power ampli¬ 
fication using push pull transformers. 

















































CHAPTER V 


USE OF PARTS IN RECEIVING 

SETS 

41. “A” BATTERY: The “A” battery is the one 
used to light the filament of the audion bulb. The letter 
“A” has no other significance than that of a definition 
of the battery. 

Certain types of bulbs use a considerable amount of 
current, in which case it is necessary to have an ”A” bat¬ 
tery which is similar to the batteries used for starting and 



Fig. 56—Radio “A” Storage Battery. 


lighting an automobile. Other bulbs use such a small 
amount of current that it is possible to run them econom¬ 
ically with a battery of the dry cell type. 

Wet batteries are rated in ampere hours. For instance, 
the most commonly used in radio work is the 80 ampere 

94 







RADIO THEORY SIMPLIFIED 


95 


hour battery. This means that it is possible to draw one 
ampere from this battery for 80 hours of intermittent 
service, without recharging it. As explained under bulbs, 
the type 200 or 300 uses from one to one and a quarter 
amperes so that a battery of the 80 ampere hour type will 
run a bulb of this kind from 60 to 70 hours. This, of 
course, is if the battery is fully charged to begin with and 
the bulb is only used a few hours every day. There are 
other types of 6 volt bulbs which use only one quarter of 
an ampere and of course the battery will run these for 
some time. Nearly all types of wet batteries have a volt¬ 
age of two volts per cell and if the battery has three cells 
it has six volts, and if six cells, it has twelve volts. Some¬ 
times automobile batteries are of the twelve volt type, 
so care must be taken with these to use only three cells 
with a six volt bulb. The construction of the radio and 
automobile battery is practically the same so that an 
automobile battery can be used for radio work. If buying 
a battery for radio use only, however, it is advisable to 
have one made specially for this purpose, as an automo¬ 
bile battery is built for a heavier load for short periods 
of time where a radio battery is built for a small load over 
a longer time. 

“A” batteries of the dry cell type can be used on all 
bulbs using a quarter hour ampere or less. The average 
dry cell has a rated voltage of one and a half volts and 
.25 amperes for 100 hours. When the bulbs used require 
more than one and a half volts, it is necessary to connect 
two or more cells in series. 

42. AERIAL INSULATOR: The importance of a 
well insulated aerial has been explained previously. The 
efficiency of an aerial is only as good as the insulation 
used to support same. Much more care must be taken 


96 


RADIO THEORY SIMPLIFIED 


with the insulation of a transmitting aerial than is nec¬ 
essary with a receiving antenna. 

With a receiving antenna, all that is necessary is to use 
good insulators of the type shown. At times, common 
2-wire cleats, such as are used for common house wiring, 
will do although a porcelain insulator that is glazed is 
much more efficient in wet weather than one of the un¬ 
glazed type. 




Fig. 57 —Aerial Insulator* 


43. AERIAL WIRE: Many new and novel kinds of 
wire have been placed on the market for use in receiving 
aerials. Tests have shown that these were superior only 
from a sales angle. The buyer was made to believe that 
because of some fancy twist or turn in the way the small 
wires were stranded and in the way they were fastened 
together, that it was superior as a carrier of high fre¬ 
quency current. Tests made by some of the more experi¬ 
enced engineers of the country have proven that these 
claims were not always based upon facts. It may be said 
that for all ordinary purposes the solid No. 14 B & S gauge 









RADIO THEORY SIMPLIFIED 


97 


bare copper wire will give as good results as many of the 
high priced kinds. Steel wire which is given a copper 
plating is also satisfactory and also has the added advan¬ 
tage of being much stronger. It has also been brought 
out that enameling of the wire keeps it from corroding 
and consequently keeps down skin resistance. This enam¬ 
eled wire is to be had both stranded and solid. 

43A. “B” BATTERIES: “B” Batteries, as well as 
“A” batteries, are of two kinds; wet and dry; but as the 
plate current required for each vacuum tube is very small 
the most commonly used type is a number of dry cells 



Fig. 58 

Dry “B” Battery. 


hooked up in series. These can be purchased in block 
form from 4}^ to 113 volts and of various capacities. 
There is not much to be said of this kind of a dry cell bat¬ 
tery excepting that some makes have a much longer life 
than others and that batteries will become deteriorated or 











































98 


RADIO THEORY SIMPLIFIED 


discharged whether used or not. A good battery should 
have a shelf life of at least six months. Under ordinary 
use they should last the same length of time. Poor “B” 
batteries cause noises and sometimes frying sounds heard 
in the receivers is being caused by defective “B” batteries. 
These noises are oftentimes mistaken for static. 

It is best to discard dry “B” batteries when they test 
70 percent of normal. 

44. “B” BATTERIES—CHARGEABLE: Charge¬ 
able “B” batteries have the advantage of being very quiet 
and can also be kept up to efficiency by having them 



Fig. 59—Storage “B” Battery. 


charged from time to time. It is always advisable to have 
a voltmeter to test batteries occasionally as this is the 
best way to tell whether or not they are giving efficient 
service. 

The wet or chargeable batteries are sold singularly or 
in units of twelve cells or twenty-four volts. 




















RADIO THEORY SIMPLIFIED 


99 


45. BATTERY CHARGERS: Numerous manu¬ 
facturers are making battery chargers which can be used 
in the home for charging both radio and automobile bat¬ 
teries. If the electric current used for lighting purposes 
is D. C. or direct current, a battery charger is not neces¬ 
sary as a few lamps in series with a 110 vclt line is all 
that is necessary to charge an ordinary radio or auto¬ 
mobile battery. When the current used is A. C. or 




Fig. 60—Storage “A” and “B” Battery Charger. 


alternating current, it is necessary to have some sort of 
mechanical, chemical or vacuum tube rectifier. Mechan¬ 
ical types generally have a much higher charging rate but 
are very noisy. Chemical chargers are the cheapest kind 
but ordinarily have a low charging rate and are very dis¬ 
agreeable to have around. The vacuum tube type has 
many superior advantages although for daily work they 
are quite expensive. A battery charger which is con¬ 
structed so that the “B” batteries can also be charged is 
to be recommended. 









100 


RADIO THEORY SIMPLIFIED 


46. BEZELS: Bezels, which are sometimes used in 
radio panels, serve two purposes; first, as a ventilator for 
the cabinet, allowing the heat generated by the bulbs to 
escape; second, to enable the operator to see if the tubes 
in the set are burning. Bezels of this type are more neces¬ 
sary with the old time bulbs drawing a heavy current and 
consequently generating more heat than with the newer 
type of bulb which uses very little current and so does not 



Fig. 61—Ventilator or Bezel. 


require the ventilation because very little heat is gener¬ 
ated. The later bulbs also light up very little and con¬ 
sequently the operator cannot see whether they are lit or 
not, even when using a bezel, so the use of the bezel is not 
as universal or as necessary as it used to be. 

Cutting the holes in the panel for these bezels offers 
quite a difficult job, but special tools can be had for this 
purpose, or this can be done with an ordinary extension 
wood bit. 


RADIO THEORY SIMPLIFIED 


101 


47. “C” BATTERIES: "C” Batteries are sometimes 
used with a detector instead of the common grid conden¬ 
ser and grid leak. This practice has practically ceased 



and now the only place they are considerably used is in 
connection with amplifying bulbs. “C” batteries are also 
called bias batteries or grid bias batteries. 

48. CHOKE COILS: Choke Coils are used in trans¬ 
mitting sets. There are many kinds and their main re¬ 
quirements is that they have a sufficient number of turns 
to choke out the passage of radio frequency current and 
still allow the audio frequency current to pass. 

49. CONDENSERS—FIXED: Fixed condensers 
are used in many places in a receiving set. Nearly all 
hook-ups require a grid condenser and in some instances 
it is advisable to use one across the phone terminals. 
Fixed condensers are made by using some type of metal 
such as tin foil or thin brass separated with mica or paper. 
The capacity of a condenser is determined by the plate 
area and by the thickness and strength of the dielectric 
used. They are rated in farads but as the farad is too 














102 


RADIO THEORY SIMPLIFIED 


large a unit for practical purposes, the use of microfarads 
and micromicrofarads is common. A microfarad is one 
millionth of the farad and the micromicrofarad is one 



Fig. 63—Fixed Condenser. 


millionth of the microfarad. A fixed condenser of .001 
MFD capacity would be one one-thousandth of a micro¬ 
farad. 

50. CONDENSERS—VARIABLE: Variable con¬ 
densers operate in the same manner as the fixed conden¬ 
sers except that they have some means provided of vary¬ 
ing the capacity. They nearly all use air as a dielectric, 
although mica and other materials are sometimes used 
to keep the plates of the condenser from touching. The 
closer the plates are together, the greater the capacity 
per square inch of the plate area. 

The material used to insulate one set of plates from the 
others has a great deal to do with the efficiency of the con¬ 
denser. If this material is poor, the electrostatic current 











RADIO THEORY SIMPLIFIED 


103 


will creep across the dielectric insulation instead of going 
through the dielectric between the plates. The variable 
condenser which has a very small amount of insulation to 



Fig. 64—Variable Condenser. 


hold two sets of plates together will have a higher effi¬ 
ciency than one which uses a great deal of insulating ma¬ 
terial in the electrical field. 

51. CRYSTAL DETECTOR: The use of the 
crystal detector has been explained previously; the follow¬ 
ing are the different kinds of minerals used for this pur¬ 
pose. The most commonly used are galena and silicon 









104 


RADIO THEORY SIMPLIFIED 


and the others are iron-pyrites, carborundum, zincite and 
ferron. Holders for these minerals are of many different 
types and the only requirements is that the contract is 
made the proper way. 



Fig. 65—Crystal Detector. Adjustable. 


52. DIALS: The only object of the dial is to act as a 
kind of knob to turn the shafts of the various parts of the 



set, such as the vario-coupler, variometer, variable con¬ 
denser, etc. They are nearly always calibrated so that 
the operator can get a reading of the position of the 
apparatus. 










RADIO THEORY SIMPLIFIED 


105 


Some of the better types are also geared to give a ver¬ 
nier adjustment. Dials also insulate the operator’s hand 
from the metal shafts of these parts so that the better 
kinds are made of some good dielectric material. 

53. GRID CONDENSERS: The use of the grid con¬ 
denser has been explained previously. These are nearly 
always of small capacity from .00025 to .0005. These are 
also sold in one unit complete with grid leak. It is better 
if some method can be had of changing or varying the 
resistance of the grid leak. 



-—.- 

MM 


—r II —r=-~-~ _ 







Fig. 67—Grid condenser. 


Grid Leaks can be purchased as a separate unit with a 
fixed resistance or with some method of varying their 
resistance. When the resistance is fixed and they are put 
up in cartridge form, mountings can be had whereby they 
can be changed easily. Many times operators use a com¬ 
mon piece of cardboard and a pencil mark. If care is 
taken to get this mark around the terminals so that it 
makes a good contact, it will work as well as any and can 
be varied by making the mark lighter or heavier. India 
ink also makes a good leak and is oftentimes used across 
a piece of cardboard in place of a pencil mark. 

54. GRID LEAKS: The use of the grid leak in con¬ 
nection with the grid condenser has been explained thor¬ 
oughly in Chapter 2. Grid leaks of many kinds can be 








106 


RADIO THEORY SIMPLIFIED 


had. Quite often a fixed leak of the cartridge type is 
furnished with the grid condenser and clips are fastened 



r/*so vnRmQLE: 

Fife. 68—Grid Leak. 


on the condenser in which this cartridge leak can be 
mounted and very easily changed. 

55. GROUND CLAMPS: Ground clamps are used 
to make a good connection between the ground wire and 
water pipe or the pipe going into the ground. Just wrap¬ 
ping the wire around the pipe will not make a good con¬ 
nection and it is very difficult to solder a wire to a water 
pipe, but the pipe can be cleaned, the ground clamp fas¬ 
tened securely in place, and the wire soldered to the 
clamp. 



Fig. 69—Ground Clamp. 
















RADIO THEORY SIMPLIFIED 


107 

56. HONEYCOMB COILS: The word honeycomb 
coils is generally applied to all coils of similar make al¬ 
though it should be used only in connection with the coils 
made by one company. Coils of this type make very 
good inductances and a great many turns of wire can be 
wound in a small space. Sometimes these are tapped but 
most generally they have only the two ends which can be 
connected to the circuit. They are mounted in many 
different ways: sometimes on the front of the panel and 
sometimes on the back. Mounting plugs and brackets 



Fig. 70—Honeycomb or Duolaterai Coll. 


can be had which have the proper contacts whereby the 
coils can be changed quickly. When this type of coil is 
used to receive both long and short waves, changing of 
these coils is often necessary. The only method of tuning 
an inductance coil which is not tapped is with a variable 
condenser shunted across or in series with the coil. 







108 


RADIO THEORY SIMPLIFIED 


Often, coils of the honeycomb type are used for loading 
the primary circuit in order to receive stations trans¬ 
mitting very long waves. The efficiency of these as in¬ 
ductance coils is very good. 

57. HYDROMETER: By having a hydrometer the 
operator of a receiving set can determine the conditions 
of his wet “A” or “B” batteries. When a storage battery 
becomes charged, the active materials of the plates forms 
acid which goes into solution with the water in the jar and 
we have what is known as a high specific gravity. This 



Fig. 71—Hydrometer or Storage Battery Tester. 


can be measured with a hydrometer. As the battery is 
used, the acid is lost in reaction with the plates and the 
acid in the water is lessened and then there is what is 
known as a low specific gravity. Most batteries are 
charged when the hydrometei reads 1250 and discharged 
when it reads below 1050. The hydrometer tells the con¬ 
dition of the battery much better than a voltmeter, as the 
specific gravity changes in a greater proportion than does 
the electromotive force upon charge and discharge. 

58. INDUCTANCE SWITCHES: Inductance 
switches, such as shown in Fig. 72 are often times used in 
place of contact points and switch arms. These are gen¬ 
erally arranged so that they do not require more than one 
to three holes in the panel, thus saving considerable work 











RADIO THEORY SIMPLIFIED 


109 


for the builder of a set. Inductance switches of this type 
should always have a pointer or other indicating device 
for registering the position of the contact. If this is avail¬ 
able, direct readings can be taken of the position of the 




contact arm and reference can be made to this reading 
when it is wished to pick up the same station on two dif¬ 
ferent occasions. 

59. JACKS: Jacks are used merely to make it easy 
to change from one stage of amplification to another. 
There are also filament control jacks constructed so that 
when the telephone plug is inserted in the jack, the fila¬ 
ment of the bulb in that particular stage of amplification 
will light and when the plug is removed, the light will go 
out. 




UO RADIO THEORY SIMPLIFIED 

When more than one jack is used, they should be of the 
two circuit type, the same as shown, except that in the 




Fig. 73—Jacks. 



last stage a single circuit jack can be used. The two-cir¬ 
cuit jack is so made that when the plug is removed, con¬ 
nection is made to the next stage. 

60. LOOSE COUPLERS: Loose couplers were one 
of the first pieces of apparatus used for tuning, in radio 
circuits. They are also oftentimes called transformers. 
All of the old timers, at some time used a loose coupler 
and they always proved very efficient for use over a wide 































RADIO THEORY SIMPLIFIED 


111 


band of wave lengths. They are now being discarded in 
favor of the more compact forms of inductances such as 
the honeycomb coil, spider web coil, vario-coupler, and 
variometer. There are still a few in use, however, and it 
will be found that they can be adapted to many circuits 
using either a crystal detector or audion bulb. 

61. LOOP ANTENNAE: Loop or coil antennae are 
becoming more and more popular as advancement is 
made in building efficient radio frequency amplifying 
units. They have the advantage of being compact, port¬ 
able, and have what is known as directional qualities. 



Fig. 74—Loop Antenna. 


This means that they will become excited when pointed 
directly at the station sending out the radio wave. The 
loop is generally shunted by a large condenser and this is 
generally the only tuning adjustment, although taps are 
sometimes taken off and then the number of turns in use 
can be varied. 


















112 


RADIO THEORY SIMPLIFIED 


62. LOUD SPEAKING UNITS: Loud speaking 
units are in general use today and as the radio industry 
advances they will become more and more common. Most 
radio receiving sets are used to receive programs from 



Fig. 75—Loud Speaker or Radio Horn. 


broadcasting stations and when listening to these it is 
much more pleasant to be able to hear without the use of 
head phones. There has been a big advancement in the 
manufacture of this type of apparatus and some of the 
later models give very good reproductions. 

The first of these put on the market were a great deal 
like the first phonographs and the noise which they made 
was anything but musical. They are still far from being 
perfect but with the strides that are being made, indica¬ 
tions are that soon they will be equal in accoustical quali¬ 
ties to the better types of phonographs. 


RADIO THEORY SIMPLIFIED 


113 


Some kinds of loud speakers use what is known as field 
excitation, meaning that they must be connected to the 
4 ‘A” battery. This strengthens the signal and gives it a 
much greater volume. Many types are used in connection 
with power amplification. Power amplification consists 
of one or more bulbs used with a special kind of trans¬ 
former which gives a stronger signal without distortion. 



Fig. 76—Phonograph Loud Speaking Attachment. 


There are many horns on the market which can be used 
with head phones. These are not as satisfactory as a 
specially built loud speaking unit as the phones were not 
designed to stand the stronger current which is present 
after one or more stages of audio frequency amplification 
have been used. 

Another popular type of loud speaking unit used is the 
one which can be fastened to a phonograph. These units 
were made to take a strong current and most of them have 
a method of adjusting the diaphragm so that the tone 
will be very clear. 



114 


RADIO THEORY SIMPLIFIED 


63. PANEL MARKERS: Panel markers come in 
many different types. Binding posts are sometimes 
furnished with tops which have the markings on them 
where they can readily be seen. One disadvantage of the 
majority of these is that these tops can be taken off and 
care must be used not to reverse them in putting them 
back. There are many other types of metal markers 
which can be fastened under the metal binding posts. 


yov yov 


AERIAL 


QROUND 



A- BAIT 


b-batt! 


Fig. 77—Pane! Markers. 


Other panel markers in use are the transfers which are 
easy to put on and some of the later types brought out 
have the appearance of the engraved panel. A nice job 
of engraving is generally the best but this is a consider¬ 
able bother and for ordinary use the panel markers will 
answer the purpose. 






























RADIO THEORY SIMPLIFIED 


115 


64. PLUGS: Phone plugs, similar to those used in 
radio work, have been in use by the telephone companies 
in their switchboards for years. A few changes have been 
made in these, however, to adapt them for radio use. The 
plug which is used by the operator of a receiving set 
should be of the proper kind to fit the jacks which are in 



Fig. 78—Phone Plug. 


the set. Often times interrupted service is caused by 
using a plug which is not making a good contact in the 
jack. Several types of phone plugs are made which will 
accommodate one or more pairs of receivers. 

65. POTENTIOMETER: There are not so many 
potentiometers used now as have been used in the past. 












116 


RADIO THEORY SIMPLIFIED 


Several years ago, “B” battery potentiometers were in 
general use, but experience teaches us that these run down 
the “B” battery and the use of them was finally discon¬ 
tinued. “A” battery potentiometers are quite often used 
at the present time in radio frequency sets. These are 
generally of quite high resistance, 200 ohms or over, and 
when shunted directly across the “A” battery do not pass 
a sufficient amount of current to run down the “A” bat¬ 
tery to any considerable extent. If leaving the set stand 
for any great time, however, the “A” battery should be 
disconnected, either by inserting a battery switch be¬ 
tween the potentiometer and the battery or by discon¬ 
necting one of the wires fastened to the terminals of the 
battery. 

66. RESISTANCE UNITS: Various hook-ups have 
different places for installing resistance units. These 
units are built from 20 to 30 ohms up into 400 or 500 ohms 



Fig. 80—Resistance Unit. 


of resistance and are merely a type of resistance wire 
wound in compact form in order to obtain the proper 
values and allow them to go into the small amount of 
space which is available in the receiving set. Quite often 
20 or 30 ohm resistances are mounted upon the common 
6 ohm rheostat in order to give added control for bulbs 
of the 201A and 199 type. 
































RADIO THEORY SIMPLIFIED 


117 


67. RHEOSTATS: There are many and various 
types of filament rheostats and they range in size from 
four to forty ohms. The rheostat is inserted between the 
battery and the filament of the tube in order to control 
the voltage applied to the tube. By thus having this 
variation, the heat of the bulb can be controlled, which 
in turn controls the flow of electrons between the filament 
and plate. This adjustment is sometimes so critical that 
a vernier of some type should be used. A vernier adjust¬ 
ment is generally no more or less than a single stand of 



VWWVWV 


Fig. 81—Filament Rheostat. 


resistance wire which is controlled by a separate knob. 
The size of rheostats to use for different types of bulbs is 
shown in the latter part of this chapter where the indi¬ 
vidual bulbs and their uses are considered. Sometimes 
rheostats should be installed in the negative lead and 
sometimes in the positive lead. The instructions which 
come with most of the audion bulbs and different hook¬ 
ups, show the proper place to install the rheostats. 





118 


RADIO THEORY SIMPLIFIED 


68. SOCKETS: There are hundreds of different 
types of sockets on the market. Some of these are very 
efficient and others are the cause of much trouble and 
annoyance in receiving sets. The socket holds the heart 
of the receiving set, the bulb, and if for any reason this is 
not held rigidly, and good connections are not made with 
all the contact points on the bottom of the bulb, trouble 
will be experienced. Also, if the binding posts on the 



T r 


Fiji. 83—Tube Socket. 


socket are not securely fastened to the springs making 
contact with the bulb, a radio set will oftentimes be noisy. 

When purchasing a socket a good thing to watch is that 
the outside of the shell fits the bulb snugly but not closely 
enough to make the changing of the bulb difficult. Also 
see that the springs are made of material which will keep 
a good tension on the prongs of the socket. These springs 
should also be clean, free from corrosion, and uniform. 
A little attention or tightening up of sockets in a radio set 
will oftentimes do away with troublesome noises that are 
thought to be outside interference. 















RADIO THEORY SIMPLIFIED 


119 


<59. SOCKET BRACKETS: Socket brackets such 
as are pictured, afford a very convenient method of 
mounting the socket and transformer to the panel. Many 



Fig. 83—Socket and Transformer Brackets. 


times a sub-base which is made of wood or some other 
panel material, is used to mount the sockets, but these 
are generally more or less of a bother and if socket brack¬ 
ets similar to those shown in the drawing are used, the 
sub-base is unnecessary. 

70. SOLDERING LUGS: Since the introduction of 
heavy bus-bar wire, soldering lugs have come into general 
use. The ordinary terminals on radio apparatus and the 



120 


RADIO THEORY SIMPLIFIED 


screws used in binding posts are not heavy enough to 
make a good connection with the heavy bus-bar wire, so 
soldering lugs, similar to those shown in the drawing, are 
fastened to the terminals and the bus-bar wire soldered 
to them. 



Fig. 84—Soldering Lugs. 


71. SPIDER WEB COILS: Spider web coils are a 
type of inductance which is used for many purposes. 
Sometimes they are tapped and then the number of turns 
on the coil can be varied but generally they are tuned by 
the use of variable condensers and also by couplings or 
changing their relations to each other. 

These coils are made in various types. Sometimes a 
form is used to wind the wire and at other times the wire 
is wound on a form and some type of adhesive paint is 
applied which will hold the wire together when the form 
is removed. Other spider web coils are wound on a form 
and then held together by the use of string. These coils 
are generally of high efficiency and wonderful results can 


RADIO THEORY SIMPLIFIED 


121 


be obtained by the use of them for tuning purposes. They 
can also be used as radio frequency transformers. 



72. TRANSFORMERS — AUDIO FREQUENCY: 
As explained before, audio frequency transformers are 
used to raise the voltage of the rectified audio frequency 
wave which is taken from the plate circuit of the detector 
bulb. The transformer also acts as a coupling between 
the two bulbs to keep the “B” battery plate voltage from 
being impressed directly upon the grid. The same type 
of transformer can be used to hook one or more stage of 
audio frequency amplification together. 


















122 


RADIO THEORY SIMPLIFIED 


Many questions are asked regarding the proper ratio of 
audio frequency transformers. It used to be thought 
that the higher ratio transformers were the best but 
recently the lower ratio transformers, viz., three to one 



Fig. 86—Audio Frequency Transformer. 


(3-1) four to one (4-1) and five to one (5-1), seem to be 
the most popular types. Regardless of the change in volt¬ 
age which a transformer will make, it will not increase the 
power which is impressed on the grid of the amplifier tube 
so that for ordinary use a transformer of the lower ratio 
will give as strong a signal and many times a much clearer 
signal, than can be had from a transformer of a higher 
ratio. Transformer ratio is the comparison between the 
number of turns of the primary and the secondary wind¬ 
ings. For instance, in a ten to one (10-1) ratio trans¬ 
former having a windings of 11,000 turns, there will be 
one thousand turns on the primary and ten thousand 


secq/vjirv: 






































RADIO THEORY SIMPLIFIED 


123 


turns on the secondary. A three to one (3-1) ratio trans¬ 
former would have two thousand seven hundred fifty 
turns on the primary and eight thousand two hnudred 
fifty turns on the secondary. 

73. TRANSFORMERS —RADIO FREQUENCY: 
The use of radio frequency transformers was explained in 
Chapter 3. There are many different types of these man¬ 
ufactured and the efficiency generally depends upon hav¬ 
ing the proper hook-up for the transformer being used. 
Also there are many different types of air core transform¬ 
ers which can be made very easily by the person who 
wishes to build a radio frequency set. Some of the later 
types of tuned radio frequency sets use transformers 



Fig. 87—Radio Frequency Transformer. 


which consist of no more or less than two inductance coils 
wound on paper or composition tubes and which are 
tuned by the use of a variable condenser. Two spider 
web or two honeycomb coils are also used for coupling the 
radio frequency bulbs together and at times there are two 
windings wound on the same form. One winding is used 
as the primary and the other as the secondary of the 
transformer. In any of these types of transformers the 
values must be right in order to give efficient results, over 
the desired wave length band. 






124 


RADIO THEORY SIMPLIFIED 


74. VARIO-COUPLERS: Vario-couplers are used 
for tuning the aerial circuit in resonance with the incom¬ 
ing radio wave. It has been explained how some method 
of tuning must be had in order to get the receiving set in 
resonance with the wave which is wished to be picked up. 
Vario-couplers are generally tapped and the number of 



Fig. 88—Vario-Coupler. 


turns of wire can be varied as well as the coupling or the 
distance or position between the rotor and the tapped 
coil can be varied. When using a vario-coupler in a two 
or three circuit receiver, the rotor is generally tuned by 
shunting a variable condenser of proper capacity across 
this. 

75. VARIOMETERS: Variometers consist of an 
inductance device which is made up of stator windings 
and windings on the rotor. When this is used as a tuning 
device or as a variable inductance in the plate circuits to 
cause regeneration, the rotor is wired in series with the 
stator windings and electric fields set up around these 
separate windings will either buck or help each other so 





RADIO THEORY SIMPLIFIED 


125 


that a variable amount of inductance can be had by turn¬ 
ing the rotor of the variometer into different positions. 



Fig. 89—Variometer. 


Some of the later types of hook-ups use a split vario¬ 
meter which makes a two circuit tuning device of it. 
When used in this way the two windings are not con¬ 
nected in any way. 

76. BULBS USED IN RECEIVING SETS: The 
balance of this chapter will be taken up with the explana¬ 
tion of several different types of vacuum tubes and their 
different characteristics as given by the manufacturers. 
There are so many different types of bulbs made that it is 
confusing to the amateur to know which one of them will 
fit his particular needs. The recommendations which are 
given need not be followed but are based on experiments 
which have been made from time to time on broadcast 















126 


RADIO THEORY SIMPLIFIED 


reception. Different operators will have their likes and 
dislikes and so some of these recommendations will be 
probably disagreed with. 

Since the original DeForest patent has expired, a great 
number of new bulbs have been placed on the market, 
but these have not been out long enough for proper tests 
to have been made; therefore, A DISCUSSION OF 
THESE WILL BE OMITTED. 



Fig. 90—U. V. 199 or C 299 Audlon Bui b. 


77. RADIOTRON UV 199 and CUNNINGHAM C 
299: The Radiotron UV 199 is distributed by the Radio 
Corporation of America and the C 299 is distributed by 
E. T. Cunningham, Inc. 




























RADIO THEORY SIMPLIFIED 


127 


These bulbs are the smallest of the later types of tubes 
and works very well for use as a detector or amplifier and 
can be used with dry cells as an “A” battery. Arnyone 
who wants a portable radio or audio-frequency amplifier 
and detector will find that this type of bulb will work as 
well as any. When using this tube as an amplifier with a 
high plate voltage a grid bias battery should be used. 
This grid bias battery should be hooked in the grid 
return, as is shown in Fig. 91. The grid bias battery 
should 'Iso be of different voltage for the different plate 
voltage. The table below gives this, as well as other of 
their electrical characteristics. 


Filament Battery Voltage 
Filament Terminal Voltage 
Filament Current 
Plate Voltage: 

Detector 

Amplifier 

Grid Bias Battery: 

Plate Voltage 

Plate Voltage 

Rheostat Used 
3 Dry Cells (4.5 Volts) 

6 Volt Storage Battery 
Grid Condenser 
Grid Leak 


4.5 Volts 
3 Volts 

.06 Amperes 

40 to 45 Volts 
45 to 90 Volts 

45 to 67.5 Volts—use 

1.5 to 3.0 Volts 

67.5 to 90 Volts—use 
3.0 to 4.5 Volts 

30 ohms 
60 ohms 
.00025 MFD 
2 to 5 Megohms 


As this tube is much smaller than a standard base, a 
special socket or adapter must be used. This tube will 
stand a much higher filament voltage than it is rated at. 
When this voltage is applied, however, electron omis¬ 
sion will cease and the bulb can be brought back to nor¬ 
mal by lighting the filament with the plate battery dis¬ 
connected. 


*TOTh 


128 


RADIO THEORY SIMPLIFIED 


78. RADIOTRON UV 201 and CUNNINGHAM 
C 301: These tubes have been superseded by the UV 
201A and the C 301A. 



Fl£. 91—Hook-up Showing Proper Place for “C” or Grid Bias Battery. 


79. RADIOTRON UV 201A and CUNNINGHAM 
C 301 A: These are two of the later type of tubes using a 




Fig. 92—Hook-up Showing Proper Connections for Grid Return. 







































RADIO THEORY SIMPLIFIED 


129 


new tungsten filament and are much more economical in 
operation, as they only use .25 of an ampere of current 
whereas the old 201 and 301 used 1.0 ampere. These 
tubes also have a very high vacuum and are the best that 
can be had for either radio or audio frequency ampli¬ 
fication. They can also be used as a detector but are not 
nearly so good as a detector bulb of the 200 and 300 type. 



Fig. 93—U V 200 or C 300 Audion Bulb. 

The filament of this bulb is very rugged in construction 
and will sometimes stand a very high voltage. Once, by 


















130 


RADIO THEORY SIMPLIFIED 


accident, 45 volts were connected across the filament for 
a short period and the tubes did not burn out. This is, 
however, not an experiment which would be advisable 
for anyone to make. 

If excessive voltage is applied to the filament, electron 
emission will cease and can be brought back to normal by 
lighting up the filament as rated voltage for one-half hour 
with the plate battery disconnected. 

When this bulb is used as a detector the grid return 
should be connected to the positive side of the “A” bat¬ 
tery and when used as an amplifier the grid return should 
be connected to the negative side of the “A” battery. The 
drawing in Fig. 92 shows how this is done. When used 
either as a detector or as an amplifier, the rheostat should 
be in the negative “A” battery lead. Sometimes a grid 
bias battery is used and the voltage of this battery should 
vary according to the plate voltage, as shown in the table 
for the UV 199 and C 299. 

Filament Battery 

Plate Voltage 
Detector 
Amplifier 
Grid Condenser 
Grid Leak 
Socket Needed 


6-volt Storage Battery 
or 4 Dry Cells 

40 Volts 
40 to 100 Volts 
.00025 MFD 
2 to 5 Megohms 
Standard Navy Base 


These tunes should be operated at the least possible 
voltage and with a six volt storage battery, the rheostat 
should be between 10-30 ohms resistance. 


80. RADIOTRON WD 11 OR C 11: The WD 11 is 
similar to the WD 12 with the exception, however, that 
the WD 12 will fit the standard navy socket whereas the 
WD 11 must have a special socket or adapter. 


RADIO THEORY SIMPLIFIED 


131 


81. RADIOTRON WD 12 OR C12: This bulb is 
sometimes called a peanut tube, although it is not in any 
sense the shape of a peanut. The elements used in this 
tube were small and so were the elements used in the old 
time peanut tube so that is probably the reason it is erro¬ 
neously called a peanut tube. The WD 11 and WD 12 



have many advantages as a detector bulb; chief of which 
is that they use very little current and low voltage, and 
can be worked with a single dry cell. They can also be 




























132 


RADIO THEORY SIMPLIFIED 


used as amplifier bulbs but it has been found that they 
are not nearly as good for this purpose as the bulb of the 
201A type. For use with a single bulb detector set, results 
are very satisfactory and oftentimes when it is impossible 



Fi£. 95—W D 12 or G 12 Audion Bulb. 


or impracticable to have a storage battery, there is a great 
advantage in using a bulb of the dry cell type. They are 
also much cheaper as the cost of the storage battery is 
eliminated. 






















RADIO THEORY SIMPLIFIED 


133 


Filament Battery 


1 Dry Cell or 1 2-Volt 
Cell of a Storage Battery 
1.1 Volts 
.2 Amperes 
Plate Voltage 
Over 50 Volts 
Over 100 Volts 


Filament Terminal Voltage 
Filament Current 
Grid Bias Battery 
lj^ Volt Bias Battery 
3 Volt Bias Battery 
Plate Voltage 

Detector 20 to 22.5 Volts 

Amplifier 22.5 to 45 Volts 

Rheostat Used 

6 Ohm with Vernier for Detector 
6 Ohm without Vernier for Amplifier 
Grid Condenser .00025 MFD 

Grid Leak 2 Megohms 

Socket 

WD 12 Standard Navy Socket 

WD 11 As stated previously 


For use as a detector the grid return should be con¬ 
nected to the positive side of the “A” battery and for use 
as an amplifier the negative side of the ‘‘A” battery. 

When using a dry cell as an “A” battery, the center 
post of the battery is positive and the outside post is 
negative. Care must be taken not to get the voltage 
higher than two volts on the filament. Connections are 
the same as those shown in the drawings of the UV 199 
in Fig. 92. 


82. NORTHERN ELECTRIC 215-A BULB: The 
Northern Electric type of 215-A Vacuum tube is one 
of the smallest tubes in use and will give good results 
both as detector and amplifier. They are very economical 
in operation and are well adapted to portable sets due to 


134 


RADIO THEORY SIMPLIFIED 


the fact that they require low filament current and can 
be operated on a single dry cell. This is a Canadian tube, 
it being distributed by the Northern Electric Company 
of Canada. However it can be purchased in the United 
States. 



Fig. 96—Northern Electric Type 215A Audion Bulb. 


Filament Battery 1 dry cell, 1.5 Volts 

Filament Terminal Voltage 0.8 to 1.1 Volts 


Filament Current 
Plate Voltage— 
Detector 
Amplifier 
Plate Current 
“C” Battery 
Socket 


0.25 Ampere 

17-22 Volts 
17-45 Volts 
0.7 Milliamperes 
1.5 Volts at 45 Volts 
Special 




















RADIO THEORY SIMPLIFIED 


135 


83. WESTERN ELECTRIC 216-4 BULB: The 
Western Electric 216-A tube is similar in appear¬ 
ance to the VT-2 altho the electrical characteristics are 



entirely different, This bulb is being used extensively in 
power amplifiers but may be used successfully in any 
ordinary audio frequency amplifying unit. It is not 
nearly as economical on operation as a tube of the UV 
201-A type, due to the fact that it uses more current for 
both filament and plate. 

























136 


RADIO THEORY SIMPLIFIED 


The advantages of the 216-A lie in that it will stand a 
heavier load without giving a distorted signal,. and that 
due to the low filament temperature, long life is assured 
as the tube is operated under normal conditions. The 
filament should never burn brighter than a dull red. 

Filament Battery 6 Volt Storage Battery 

Filament Terminal Voltage 6 Volts 
Filament Current 1.0 Ampere 

Plate Voltage 100-130 Volts 

Plate Current 7 to 9 Milliamperes 

Socket Standard 4 prong Navy 

Other tubes which are coming into general use and 
seem to have merits are the “Sodion”, manufactured by 
the Connecticut Telephone & Telegraph Company and 
The Meiers. The Meiers was one of the old timers but 
was temporarily withdrawn from the market, but is now 
manufactured in Canada and can again be purchased in 
the United States. 

Another tube having a general sale is the DeForest, 
made by the DeForest Telephone & Telegraph Company, 
but due to lack of cooperation on the part of the man¬ 
ufacturers, details and characteristics will have to be 
omitted. 


CHAPTER VI 


HISTORY OF RADIO ADVANCEMENT 

It may interest many radio fans to read a summary of 
the important events in radio. The first experiments 
which have any bearing on the radio industry were con¬ 
ducted in 1827 and at various times since, new discoveries 
have been made which make possible radio telephony as 
we have it today. ■< ^ 

A history of the important events in radio has been 
compiled by the Bureau of Navigation, U. S. Govern¬ 
ment, and was published by the Department of Com¬ 
merce in their “Radio Service Bulletin." As many radio 
enthusiasts probably did not get a chance to see this 
Bulletin, it is here being reprinted. This will make a 
ready reference for anyone who wished to check up on 
the dates of the important events of Radio History. 

1827 Savary found that a steel needle could be mag¬ 
netized by the discharge from a Leyden jar. 

1831 Farady discovered electromagnetic induction 
between two entirely separate circuits. 

1837 The first patent for an electric telegraph was 
taken out by Cooke and Wheatstone (London) and by 
Morse (United States). 

1838 Steinheil discovered the use of the earth return. 

1840 Henry first produced high frequency electric 
oscillations and pointed out that the discharge of a con¬ 
denser is oscillatory. 


137 


138 


RADIO THEORY SIMPLIFIED 


1842 Morse made wireless experiments by electric 
conduction through water. 

1843 Lindsay suggested that if it were possible to pro¬ 
vide stations not more than 20 miles apart all the way 
across the Atlantic there would be no need of laying a 
cable. 

1845 Lindsay made experiments in transmitting mes¬ 
sages across the River Tay by means of electricity or 
magnetism without submerging wires, using the water 
as a conductor. 

1849 Wilkins revived the same suggestions for wire¬ 
less telegraphy. 

Dr. O’Shaughnessy succeeded in passing intelligible sig¬ 
nals without metallic conduction across a river 4,200 feet 
wide. 

1862 Heyworth patented a method of conveying 
electric signals without the intervention of any contin¬ 
uous artificial conductor. 

1867 Maxwell read a paper before the Royal Society 
in which he laid down the theory of electromagnetism, 
which he developed more fully in 1873 in his great treatise 
on electricity and magnetism. He predicted the existence 
of the electric waves that are now used in wireless tele¬ 
graphy. 

1870 Von Bezold discovered that oscillations set up 
by a condenser discharge in a conductor gave rise t& 
interference phenomena. 

1872 High ton made various experiments across the 
River Thames with Morse’s method. 

1879 Hughes discovered the phenomena on which 
depend the action of coherer. The coherer was later used 
practically by Marconi. 


RADIO THEORY SIMPLIFIED 


139 


1880 Trowbridge found that signaling might be car¬ 
ried on over considerable distances by electric conduction 
through the earth or water between places not metal¬ 
lically connected. 

1882 Bell’s experiments with Trowbridge method on 
the Potomac River resulted in the detection of signals at 
a distance of 1J4 miles. 

Professor Dolbear was awarded a United States patent 
in March 1882, for wireless apparatus in connection with 
which he made the statement that “electrical communi¬ 
cation, using this apparatus, might be established be¬ 
tween points certainly more than one-half mile apart, but 
how much farther I can not say.” It appeared that Pro¬ 
fessor Dolbear made an approach to the method that 
was, subsequently in the hands of Marconi, to be crowned 
with success. 

1883 Fitzgerald suggested a method of producing 
electromagnetic waves in space by the discharge of a con¬ 
ductor. 

1885 Edison, assisted by Gillilaud, Phelps and Smith 
worked out a system of communication between railway 
stations and moving trains by means of induction and 
without the use of conducting wires. Edison took out 
only one patent on long-distance telegraphy without 
wires. The application was filed May 23, 1885, at the 
time he was working on induction telegraphy, but the 
patent (No. 465971) was not issued until December 20, 
1891. In 1903 it was purchased from him by the Marconi 
Wireless Telegraph Company. 

Preece made experiments at Newcastle-on-Tyne which 
showed that in two completely insulated circuits of square 
form, each side being 440 yards, placed a quarter of a mile 
apart, telephonic speech was conveyed from one to the 
other by induction. 


140 


RADIO THEORY SIMPLIFIED 


1886 Dolbear patented a plan for establishing wire¬ 
less communication by means of two insulated elevated 
plates, but there is not evidence that the method pro¬ 
posed by him, did or could, effect the transmission of sig¬ 
nals between stations separated by any distance. ,1 

1887 Hertz showed that electromagnetic waves are 
in complete accordance with the waves of light and heat, 
and founded the theory upon which all modern radio 
signaling devices are based. 

Heaviside established communication by telephonic 
speech between the surface of the earth and the subter¬ 
ranean galleries of the Broomhill Collieries, 350 feet deep, 
by laying above and below ground two complete metallic 
circuits, each about 2miles in length, and parallel to 
each other. 

1889 Thompson suggested that electric waves were 
particularly suitable for the transmission of signals 
through fogs and material objects. 

1891 Trowbridge suggested that by means of mag¬ 
netic induction between two separate and completely 
insulated circuits communication could be effected be¬ 
tween distances. 

1892 Preece adopted a method which united both 
conduction and induction as the means of affecting one 
circuit by the current in another. In this way he estab¬ 
lished communication between points on the Bristol 
Channel and at Lochness in Scotland. 

Stevenson of the Northern Lighthouse Board, Edin¬ 
burg, advocated the use of an inductive system for com¬ 
munication between the mainland and isolated light¬ 
houses. 

Branly devised an appliance for detecting electromag¬ 
netic waves, which was known as a coherer. 


RADIO THEORY SIMPLIFIED 


141 


1894 Rathenau experimented with a conductive sys¬ 
tem of wireless telegraphy and signalled through 3 miles 
of water. 

1895 Smith established communication by conduc¬ 
tion with the lighthouse on the Fastnet. 

Marconi’s investigations led him to the conclusion that 
Hertzian waves could be used for telegraphing without 
wires. 

1896 Marconi lodged his application for the first 
British patent for wireless telegraphy. He conducted 
experiments in communication over a distance of 1 % 
miles successfully. 

The first demonstration of directional wireless using 
reflectors was given in England. Experiments were con¬ 
ducted to determine the relative speed of propagation of 
light waves and the electric vibrations which actuated a 
receiver at a distance of 1J4 miles between reflectors. 

1897 March 1: Marconi demonstrated communication 
being established over a distance of 4 miles. 

March 17: Balloons were first used for the suspension 
of wireless aerials. 

July 10-18: Marconi maintained communication be¬ 
tween the shore and a ship at sea at distances up to 10 
miles. 

September and October: Apparatus was erected at 
Bath, England, and signals received from Salisbury, 34 
miles distant. 

November 1: First Marconi station erected at the 
Needles, Alum Bay, Isle of Wight. Experiments were 
conducted covering a range of 14J4 miles. 

December 6: Signals transmitted from shore to a ship 
at sea, 18 miles distant. 


142 


RADIO THEORY SIMPLIFIED 


December 7: First floating wireless station was com¬ 
pleted. 

1898 June 3: The first paid radiogram was trans¬ 
mitted from the Needles (Isle of Wight) station. 

July 20-22: Events of the Kingstown regatta in Dub¬ 
lin reported by wireless for Dublin newspaper from 
steamer Flying Huntress. 

1899 April 22: The first French gunboat was fitted 
with wireless telegraph apparatus at Boulogne. 

July: During the naval manoeuvres three British war¬ 
ships equipped with Marconi apparatus interchanged 
messages at distances up to 74 nautical miles (about 85 
land miles). 

The international yacht races which took place in 
September and October were reported by wireless tele¬ 
graphy for the New York Herald. At the conclusion of 
the races series of trials were made between the United 
States cruiser New York and the battleship Massachu¬ 
setts, signals being exchanged between the vessels at dis¬ 
tance up to 36 miles. On the return journey from America 
Marconi fitted the steamship St. Paul with his apparatus, 
and on November 15 established communication with 
the Needles station when 36 miles away. Reports of the 
progress of the war in South Africa were telegraphed to 
the vessel and published in a leaflet entitled “The Trans¬ 
atlantic Times,” printed on board. 

1900 February 18: The first German commercial 
wireless station w r as opened on Borkum Island. 

February 28: The first German liner fitted with wire¬ 
less apparatus communicated with Borkum Island over 
a range of 60 miles. 

November 2: The first wireless land station in Bel¬ 
gium was finished at Lapanne. 


RADIO THEORY SIMPLIFIED 


143 


Between 1900 and 1905 Dr. De Forest was granted 
numerous patents in the United States and other coun¬ 
tries for inventions connected with wireless telegraphy. 

1901 January 1: The Bark Medora was reported by 
wireless as waterlogged on Ratel Bank. Assistance was 
immediately sent. 

January 19: The Princesse Clementine ran ashore, 
and news of the accident was telegraphed to Ostend by 
wireless. 

February 11: Communication was established be¬ 
tween Niton Station, Isle of Wight, and the Lizard sta¬ 
tion, a distance of 196 miles. 

March 1: A public wireless telegraph service was in¬ 
augurated between the five principal islands of the Ha¬ 
waiian group, viz, Oahu, Kauai, Molaki, Maui, and Ha¬ 
waii. 

October 15: The first fan aerials were erected for ex¬ 
periments between Poldhu and Newfoundland. 

December 12: The letter “S” was received by Marconi 
from Poldhu, England, at St. Johns, Newfoundland, a 
distance of 1,800 miles. 

Prof. R. A. Fessenden applied for United States patent 
on September 28 for “Improvements in apparatus for the 
wireless transmission of electromagnetic wave, said im¬ 
provements relating more especially to the transmission 
and reproduction of words or other audible signals.” It 
appears that in connection with this apparatus there was 
contemplated the use of an alternating-current generator 
having a frequency of 50,000 cycles per second. Profes¬ 
sor Fessenden was granted a number of United States 
patents between 1899 and 1905 covering devices used in 
Connection with radio telegraphy. 


144 


RADIO THEORY SIMPLIFIED 


1901-1904 During this period Dr. John Stone was 
granted more than 70 Unired States patents covering 
radiotelegraphy. 

1901-1905 More than 40 United States patents were 
granted to Harry Shoemaker covering certain apparatus 
used for radio communication. 

1902 February: Steamship Philadelphia, American 
Line, received messages a distance of 1,551}^ statute 
miles and received Morse signals up to a distance of 2,099 
statute miles from Poldhu station, Cornwall, England. 

June 25: The first moving wire magnetic detector 
actuated by clockwork was installed on the Italian cruiser 
Carlo Alberto. 

July 14-16: Marconi received messages from Poldhu 
on the Italian cruiser Carlo Alberto, lying at Cape Skagen, 
a distance of 800 miles; and at Kronstadt, 1,600 miles. 

December: On the 17th the first wireless message was 
transmitted across the Atlantic. On the 18th wireless 
messages were dispatched from Cape Breton station to 
King Edward VII. 

1903 January 19: President Roosevelt sent a trans- 
Atlantic radiogram to King Edward via Cape Cod and 
Poldhu stations. 

March 30: First transoceanic radiogram was published 
in the London Times. 

August 4: First International Radiotelegraphic Con¬ 
ference was held at Berlin. 

Poulsen patented the improved arc oscillation genera¬ 
tor, using a hydrocarbon atmosphere and a magnetic field. 

1904 January 20: The first press message was trans¬ 
mitted across the Atlantic. 


RADIO THEORY SIMPLIFIED 


145 


August 15: The wireless telegraph act of Great Britain 
was passed. 

November 16: Dr. J. Ambrose Fleming took out his 
original patent No. 24850 for thermionic valves. 

1905 In October of this year erection of Clifen, Ire¬ 
land, high-power radio station was commenced. 

1906 Doctor De Forest was granted a patent on 
January 18 for a vacuum rectifier, commercially known 
as the audion. 

Second International Radiotelegraphic Convention 
was held at Berlin, and a convention was signed by a 
majority of the principal countries of the world. 

Dunwoody discovered the rectifying properties of car¬ 
borundum crystals and Pickard discovered the similar 
properties of silicon crystals. These discoveries formed 
the basis of the widely used crystal detectors. 

1907 October 17: Trans-Atlantic stations at Clifden 
and Glace Bay were opened for limited public service. 

1908 February 3: Trans-Atlantic radio stations were 
opened to the general public for the transmission of mes¬ 
sages between the United Kingdom and the principal 
towns in Canada. 

In carrying out his invention Professor Fessenden con¬ 
structed a high-frequency alternator with an output of 
2.5 kilowatts at 225 volts and with a frequency of 70,000 
cycles per second. Later Professor Fessenden reported 
successful wireless telephonic communication between 
his station located at Brant Rock, Mass., and Washing¬ 
ton, D. C., a distance of about 600 miles. 

1909 The steamship Republic, after colliding with 
the steamship Florida off the coast of the United States 
on January 23, succeeded in calling assistance by wireless, 
with the result that all her passengers and crew were 
saved before the vessel sank. 


146 


RADIO THEORY SIMPLIFIED 


1910 The steamship Principessa Mafalds received 
messages from Clifden at a distance of 4,000 miles by day 
and 6,735 miles by night. On April 23 the Marconi Trans- 
Atlantic (Europe-Ainerica) service was opened. 

June 24: Act approved by the United States Govern¬ 
ment requiring radio equipment and operators on certain 
passenger-carrying vessels. 

1911 July 1. Radio service organized in Department 
of Commerce and Labor to enforce the act of June 24, 
1910. 

1912 F. A. Kolster, of the Bureau of Standards, in¬ 
vented and developed the Kolster decremeter, which is 
used to make direct measurements of wave length and 
logarithmic decrement. This instrument has been used 
by the radio service of the Department of Commerce 
since it was invented. 

Early in the year the American Marconi Co. absorbed 
the United Wireless Co., of the United States. 

In February the Marconi Co. procured the patents of 
Bellini and Tosi, including those for the wireless direction 
finder. 

On February 9, the Australian Commonwealth station 
was opened. 

On April 15, the steamship Titanic, on her maiden voy¬ 
age, struck an iceberg and sank, but, owing to the prompt 
wireless call lor assistance, the lives of more than 700 of 
her passengers were saved. 

The International Radiotelegraphic Conference opened 
in London on June 4 and approved important regulations 
to have uniformity of practice in wireless telegraph serv¬ 
ices. On July 5 the International Radiotelegraphic Con¬ 
vention was signed at London. 


RADIO THEORY SIMPLIFIED 


147 


July 23: Act approved by the United States Govern¬ 
ment extending act of June 24, 1910, to cover cargo ves¬ 
sels and requiring auxiliary source of power, efficient 
communication between the radio room and the bridge, 
and two or more skilled radio operators in charge of the 
apparatus on certain passenger-carrying vessels. 

August 13: Act approved by the United Government 
licensing radio operators and transmitting stations. 

1913 F. A. Kolster submitted to the Government a 
paper pointing out the advantages of certain applications 
of radio signaling for use at lighthouses, light-ships, and 
life-saving stations, especially in time of fog. 

During this year the Governments of France and the 
United States experimented between the Eiffel Tower 
station and Washington by wireless to procure data for 
comparing the velocity of electro-magnetic waves with 
that of light. 

In June, a wireless telegraph bill was presented to the 
Ottawa Parliament and passed under the title “Radio¬ 
telegraph Act of Canada.” 

On October 11, the Volturno was burned in mid-Atlan¬ 
tic, and in response to the wireless appeal 10 vessels came 
to the rescue, 521 lives being saved. 

On November 24, the first practical trials with wireless 
apparatus on trains were made on a train belonging to 
the Delaware, Lackawanna & Western Railroad. 

The station at Macquerie Island was the means of 
keeping Doctor Mauson the Australian explorer, in touch 
with the outer world. Radio dispatches were published 
in a small journal which was established, called the Adelle 
Blizzard. 

November 12: Safety at Sea Conference held in Lon¬ 
don. At this conference the use of radio received appro¬ 
priate consideration. 


148 


RADIO THEORY SIMPLIFIED 


November 24: The first practical trials with wireless 
apparatus on trains were made, messages having been 
received and transmitted on board trains. 

1914 Experiments in wireless telephony were carried 
out between several vessels lying at anchor five-eighths of 
a mile apart, ordinary receivers being used with success. 
The wireless telephone experiments were continued be¬ 
tween two warships on the high seas, and the reception 
was consistently good over a distance of 1834 miles. Suc¬ 
cessful wireless telephone communications were effected 
later, using only very limited energy between vessels on 
the high seas 44 miles apart. Thes experiments were 
repeated where land intervened between the communi¬ 
cating vessels, and in this case again excellent results 
were obtained. On this day radiotelephonic communi¬ 
cation was constantly maintained for 12 hours. 

On April 15, at Godaiming, a memorial was unveiled to 
the memory of Jack Philips, chief radio operator of the 
ill-fated Titanic, who died at his post when the vessel 
foundered in mid-Atlantic on the 15th of April, 1912. 

A new departure in the application of radiotelegraphy 
to the safety of life at sea was the equipment of the motor 
lifeboats of the steamship Aquitania with radio apparatus. 

High powered transoceanic stations were completed at 
Carnarvon, Wales, Belmar, Honolulu, and San Francisco 
during the autumn of 1914. The Honolulu-San Fran¬ 
cisco stations were opened to public service September 
24. The Tuckerton-Eilvese and Sayville-Nauen stations 
were in operation about this time. 

Most of these stations made use of the latest develop¬ 
ments in the art, using undamped and long waves as pro¬ 
duced by the Poulsen arc and the radio frequency alter¬ 
nator. 

On October 6, E. H. Armstrong was issued a patent 
covering the regenerative circuit also known as the feed¬ 
back and the self-heterodyne circuit. 


RADIO THEORY SIMPLIFIED 


149 


1915 During this year F. A. Kolster, of the Bureau of 
Standards, developed a radiocompass said to be more 
effective than that which was being used. 

On February 20, the Panama-Pacific Exposition at San 
Francisco was officially opened by President Wilson at 
Washington, through the medium of wireless telegraphy. 

On May 12, in Battery Park, New York City, the 
mayor unveiled the monument in memory of wireless 
operators who had lost their lives at the post of duty. 

On July 27 wireless communication between the United 
States and Japan was effected. Two terminal stations 
were located at San Francisco and Funabashi, nearTokio, 
and the messages were relayed through Honolulu. 

On July 28, the American Telephone & Telegraph Co., 
working in conjunction with the Western Electric Co., 
succeeded in telephoning the wireless across the American 
continent from Arlington to Hawaii, a distance of nearly 
5,000 miles. 

On October 26, the wireless telephone experiments were 
continued, communication being effected across the At¬ 
lantic from Arlington to the Eiffel Tower, Paris. 

During this year ship service was greatly improved 
through the installation of new equipment, embodying 
features of great practical value, by various operating 
companies. Efficient emergency radio transmitters came 
into wider use, owing considerably to the efforts of the 
radio service of the Department of Commerce and its 
refusal to pass inefficient equipment. Such installations 
considered as essential are safeguards to shippers and the 
seagoing public. 

1916 During the course of a severe blizzard in the 
United States during February wireless telegraphy was 
extensively used for train dispatching, as the telegraph 
wires were down. 


150 


RADIO THEORY SIMPLIFIED 


The determination of the difference in longitude be¬ 
tween Paris and Washington with the aid of radio which 
had been in progress since October, 1913, was completed 
during May, the result, expressed in terms of times, being 
5 hours 17 minutes 35.67 seconds, and has a probable 
accuracy of the order of 0.01 second. 

The initiation of the newly established trans-Pacific 
wireless service between the United States and Japan 
was celebrated on November 5, by an interchange of 
messages between the Mikado and President Wilson. 

1917 June 2, marked the “coming of age” of wireless 
telegraph in England, that is, that 21 years had elapsed 
since the registration of patent 12039 in 1896. 

1918 The trend of progress toward continuous-wave 
communication as distinct from that by damped waves 
was very marked during this year, a particular impetus 
being given by the continued development of the electron 
tube as an efficient receiver and generator of undamped 
oscillations. Steady improvement was also evident in 
the arc form of generator which was installed in many 
new high-power stations. 

Wireless telephony also progressed to a marked extent, 
particularly in the direction of reliability and increase of 
range, due mainly to the development of valve generator 
and receivers. 

In the equipment of aircraft with wireless great prog¬ 
ress was made, both in radiotelegraphy and radiotele¬ 
phony. 

At the end of the year a high-power station, erected by 
the United States Government, was opened at Croix 
d'Hins, near Bordeaux. 

In the Argentine the erection of a station destined for 
direct communication with the North American conti¬ 
nent was commenced in the vicinity of Buenos Aires. 


RADIO THEORY SIMPLIFIED 


151 


The extension in the application of wireless telegraphy 
to merchant vessels continued, and at the close of the 
year some 2,500 to 3,000 vessels of the British Merchant 
Marine carried installations. 

On July 31 the United States Government took over 
all wireless land stations in the United States, with the 
exception of certain high-power stations, which remained 
under the control of commercial companies. 

On September 22 messages transmitted from Carnar¬ 
von were received in Sydney, 12,000 miles away. Cable 
confirmations of these messages were sent forward at the 
same time but were received some hours later than the 
corresponding radio-telegrams. 

In April a high-power station was opened at Stavanger, 
Norway, for the use of the Norwegian Government. The 
station communicates with the United States. 

1919 The successful transatlantic flights of Alcock 
and Brown, of the American NC4, and of the British 
dirigible R34, during the summer of the year focused at¬ 
tention upon the application of radio for aviation pur¬ 
poses and its great value for aerial navigation. 

On June 30, 1919, there were 2,312 ship stations of the 
United States, having increased from 1,478 on June 30, 
1918. At this time new ship stations were increasing at 
the rate of 100 a month. This increase was due to the 
great number of vessels built during the war period. 

The temporary war measures relative to the instal¬ 
lation of wireless telegraph apparatus on all merchant 
vessels of 1,600 tons or over under the British flag was 
made permanent by a bill passed by the British Parlia¬ 
ment. 

In February a Spanish decree was issued to the effect 
that all sailing vessels of 500 tons or over and carrying 
50 or more passengers must be equipped with wireless 
apparatus. 


152 


RADIO THEORY SIMPLIFIED 


During the year the Radio Corporation took over the 
radio interests of the American Marconi Company. 

The war-time ban on private and experimental wire¬ 
less stations was removed. 

1920 The steady development of continuous-wave 
wireless work was continued during the year and some 
further progress made in the commercial application of 
tube apparatus. 

On January 14, a law was passed in Greece making the 
carrying of wireless apparatus obligatory on all Greek 
merchant ships of 1,600 tons gross and over, or having 
50 or more persons aboard, including crew. 

On January 25, a new high-power station was opened 
at Monte Grande, Argentine, call letters LPZ. 

Amateur radio work in this and other countries pro¬ 
gressed steadily during the year with the gradual removal 
of wartime restrictions. 

Bordeaux, France, high-power station opened. 

1921 Experiments were carried out in France with 
successful results in the application of Baudot and similar 
high-speed telegraph apparatus to radio work. 

The Noble Prize for physics was awarded this year to 
Prof. Edouard Branly for his researches in radio. 

The progress made in amateur and experimental wire¬ 
less is exemplified by the attempts made in February and 
December of this year to effect communication on short 
wave lengths between the wireless amateurs of the United 
States and Great Britain. The first attempt was unsuc¬ 
cessful, but during the second test signals from many 
American amateur stations were heard both by British 
radio amateurs and by the representative of the American 
Radio Relay League who was sent over for the tests. The 
signals were also heard in Holland. 


RADIO THEORY SIMPLIFIED 


153 


The American Radio Relay League held its first annual 
convention in Chicago, August 30—September 3, at which 
many thousands of amateurs of the United States were 
present. 

The first licenses for broadcasting stations were issued 
in September of this year. 

New York radio central station opened on Long Island. 

1922 During this year broadcasting stations increased 
rapidly in keeping with the great interest taken in the art. 

On June 7 E. H. Armstrong read a paper before the 
Institute of Radio Engineers on some recent develop¬ 
ments by him of regenerative circuits. Professor Arm¬ 
strong was granted a patent for the super-regenerative 
circuit. 

Experiments in radiotelephoning from ship to shore 
were conducted during this year. In tests from the steam¬ 
ship American it was proved possible to communicate 
with land telephone stations more than 400 miles distant 
from the ship. 

1923 On March 2, L. A. Hezeltine, of Stevens Insti¬ 
tute of Technology, presented a paper before the Radio 
Club of America on tuned radiofrequency amplification 
with neutralization of capacity coupling. Professor 
Hezeltine was granted a patent for the nonradiating 
neutrodyne receiver. 

Great progress was made during the year in the de¬ 
velopment of vacuum tubes. 

Short wave lengths were used to greater advantage 
than heretofore. 

The McMillan expedition to the polar regions had 
radio for their only means of direct communication. 
Using low power and short wave lengths their vessel, Bow- 


154 


RADIO THEORY SIMPLIFIED 


doin, communicated with several stations in the United 
States while they were frozen in thousands of miles away. 
Broadcasting concerts from United States Stations were 
heard during the long dark nights of the arctic zone. 

During the year foreign countries became interested 
in radiotelephone broadcasting. 

Broadcasting in United States heard in England, and 
vice versa. 

1924 In January radio was used in the region of the 
Great Lakes during a blizzard for dispatching trains. 

An expedition from the United States, under the leader-; 
ship of Hamilton Rice, which will explore the Amazon 
and Orinoco Rivers in Brazil and Venezuela in the interest 
of geographical science in general, will have radio as their 
only means of communication. 

On February 5, a radio program broadcast in the United 
States from Pittsburgh station of Westinghouse Electric 
& Manufacturing Company was received and rebroad¬ 
cast in England for the benefit of English stations. 

On February 23 a concert broadcast by the same sta¬ 
tion and relayed from London was heard clearly in Cal¬ 
cutta, India. 

Roger Babson, economist, estimates that during this 
year the American people will spend approximately 
$350,000,000 for radio equipment. Sales of radio equip¬ 
ment are running nearly twice as large as all kinds of 
sporting goods. 

A wireless lighthouse has been set up on an island in 
the Firth of Forth, Scotland. Wireless waves are con¬ 
centrated by reflectors into a beam which can be sent 
100 miles, giving ships their position in a fog. 


APPENDIX “A 











» 




4 














































APPENDIX “A” 


USEFUL TABLES AND CHARTS 


T HE student in his study of radio will probably find 
many symbols and abbreviations with which he is 
not familiar. If he will acquaint himself with those 
shown in this appendix, he will then be able to better 
understand the drawings shown in this book and other 
drawings of a similar nature which are found in most 
radio books and magazines. Tables are also given which 
can be used in working out radio probler s. 


TABLE OF ABBREVIATIONS 


C., Centrigrade 

cu. ft., cubic foot (feet) 

F., Fahrenheit 
ft., foot (feet) 

f. o. b., free on board (cars) 
gr. yd., gross yard(s) 
in., inch(e8) 
lb., pound 
lbs., pounds 


m.m. or m/m, milliraeter(s) 
o. d., outside diameter 
oz., ounce(s) 
sq. ft., square foot (feet) 
sq. in., square inch(es) 
sq. yd., square yards() 

•p. £r., specific gravity 
' foot (feet) 

* inch(es) 

— plus or minus 


1S7 





SYMBOLS USED IN RADIO DIAGRAMS 



158 

































































RADIO THEORY SIMPLIFIED 


159 


COPPER WIRE TABLE 


This Table will help determine the Resistance, Length, Weight and 
Area of Different Sizes of Copper Wire. 


A.W.G 

Diameter 

Area 

Weight 

Length 

RESISTANCE 

B.&S. 

Inches 

Circular 

Pounds 
per 1000 

Feet per 

Ohms per 

Ohms per 

Gauge 


Mils 

Feet 

Pound 

1000 Feet 

Pound 

0000 

0.4600 

211,600. 

640.5 

1.561 

.04901 

.00007652 

000 

0.4096 

167,800. 

507.9 

1.969 

.06180 

.0001217 

00 

0.3648 

133,100. 

402.8 

2.483 

.07793 

.0001935 

0 

0.3249 

105,500. 

319,5 

8.130 

.09827 

.0005076 

1 

0.2893 

83,690. 

253.3 

3.943 

.1239 

.0004891 

2 

0.2576 

66,370. 

200.9 

4.978 

.1563 

.0007778 

3 

0.2294 

52,630. 

159.3 

6.276 

.1970 

.0012C7 

4 

0.2043 

41,740. 

126.4 

7.911 

.2485 

.0019C6 

5 

0.1819 

33,100. 

100.2 

9.980 

.3133 

.005127 

6 

0.1620 

26,250. 

79.46 

12.58 

.3951 

.004972 

7 

0.1443 

20,820. 

63.02 

15.87 

.4982 

.007905 

8 

0.1285 

16,510. 

49.98 

20.01 

.6282 

.01257 

9 

0.1144 

13,090. 

39.63 

25.23 

.7921 

.01999 

10 

0.1019 

10,380. 

31.43 

31.82 

.9989 

.03178 

11 

0.09074 

8,234. 

24.92 

40.13 

1.260 

.05053 

12 

0.08081 

6,530. 

19.77 

50.58 

1.588 

.08035 

13 

0.07196 

5,178. 

15.68 

63.77 

2.003 

.1278 

14 

0.06408 

4,107. 

12.43 

80.45 

2.525 

.2032 

15 

0.05707 

3,257. 

9.858 

101.4 

3.184 

.3230 

16 

0.05082 

2,583. 

7.818 

127.9 

4.016 

.5136 

17 

0.04526 

2,048. 

6.200 

161.3 

5.064 

.8167 

18 

0.04030 

1,624. 

4.917 

203.4 

6.385 

1.299 

19 

0.03589 

1,288. 

3.899 

256.5 

8.051 

2.065 

20 

0.03196 

1,022. 

3.092 

323.4 

10.15 

3.283 

21 

0.02846 

810.1 

2.452 

407.8 

12.80 

5.221 

22 

0.02535 

642.4 

1.945 

514.1 

16.14 

8. SOI 

23 

0.02257 

509.5 

1.542 

648.5 

20.36 

13.20 

24 

0.0*010 

404.0 

1.223 

817.7 

25.67 

20.99 

25 

0.01700 

320.4 

0.9699 

1031. 

32.37 

S3.37 

26 

0.01594 

254.1 

0.7692 

1300. 

40.81 

53.06 

27 

0.01420 

201.5 

0.6100 

1639. 

51.47 

84.37 

28 

0.01264 

159.8 

0.4837 

2067. 

64.90 

134.2 

29 

0.01126 

126.7 

0.3836 

2606. 

81.83 

213.3 

SO 

0.01003 

100.5 

0.3042 

3287. 

103.2 

829.2 

31 

0.008928 

79.70 

0.2413 

4144. 

130.1 

539.3 

32 

0.007950 

63.21 

0.1913 

5227. 

164.1 

857.6 

83 

0.007080 

50.13 

0.1517 

6591. 

206.9 

1364. 

34 

0.006305 

39.75 

0.1203 

8312. 

260.9 

2168. 

85 

0.005615 

81.52 

0.09542 

10480. 

329.0 

3448. 
















































160 


RADIO THEORY SIMPLIFIED 


A.W.G 

Diameter 

Area 

Weight 

Length 

RESISTANCE 

B.&S. 

Inches 

Circular 

Pounds 
per 1000 

Feet per 

Ohms per 

Ohms per 

Gauge 


Mils 

Feet 

Pound 

1000 Feet 

Pound 

36 

0.005000 

25.00 

0.07568 

13213. 

414.8 

5432. 

37 

0.004453 

19.83 

0.0601 

16664. 

523.1 

8717. 

38 

0.003905 

15.72 

0.04759 

21012. 

659.6 

13360. 

89 

0.033531 

12.47 

0.03774 

26497. 

831.8 

22040. 

40 

0.003145 

9.888 

0.02990 

33411. 

1049. 

35040. 

(41)* 

0.00275 

7.5625 

0.02289 

43,700. 

13”0. 

59,900. 

(4C)* 

0.00250 

6.2500 

0.01892 

52,800. 

1660. 

87,700. 


0.00225 

5.0025 

0.01532 

65,300. 

2050. 

133,700. 

0.00200 

4.0000 

0.01211 

82,600. 

2600. 

214,000. 

(45) * 
(43)* 

0.00175 

3.0625 

0.00927 

107,900. 

3390. 

365,200. 

0.00150 

2.2500 

0.00681 

146,800. 

4610. 

676,800. 


*B. & S. Gauge numbers for the sizes smaller than No. 40 are often used, but are 
not yet fully recognized. It is best to specify these sizes by their diameters. 


COMMON RADIO ABBREVIATIONS 


flr/T. 

flNTENnri of* flzpjnu 

Qno. 

Ground 

Tcu 

Tclcp/'/qnc 

flrtp 

£Jrt/=>L/r/£R. 

Djzt 

Dztcctor 

S/jtt 

/3/7TT/ZRY 

f7.ro. 

fl/CTforsjRno. 

Pot 

f*a Tcrrr/oricT£.F? 

SJ.-r 

/?UD/0 • fj^JZQU/ZPfGY. 

THnrtS 



























RADIO THEORY SIMPLIFIED 


161 


INTERNATIONAL TELEGRAPHIC CODE 


















































W. 1 

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70 

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90 

100 

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120 

130 

140 

150 

160 

170 

173. 

180 

190 

200 

210 

220 

230 

240 

250 

260 

270 

280 

290 

300 

310 

320 

330 

340 

350 

360 

370 

380 

390 

400 

410 

420 

430 

440 

450 

460 

470 

480 

4S0 

510 

500 

520 


277 

275 

272 

270 

267 

265 

263 

260 

258 

256 

254 

252 

249 

247 

245 

243 

241 

239, 

238 

236 

234, 

232. 

230. 

228. 

227. 

225. 

223. 

222 . 

220 . 

218. 

217. 

215. 

214. 

212 . 

211 . 

209. 

208. 

206. 

205. 

204. 

202 . 

201 . 

199. 

198. 

197. 

196. 

194. 

193. 

192. 

191. 


RADIO THEORY SIMPLIFIED 


5 SHOWING THE RELATIC 
VE LENGTH TO FREQUEN 

Vave Length in Meters—Frequency in Kilocycles 


Freq. 

W. L. 

Freq. 

W. L. 

29980 

530 

565.7 

1050 

14990 

540 

555.2 

1060 

9994 

550 

545.1 

1070 

7496 

547.6 

547.6 

1080 

5996 

560 

535.4 

1090 

4997 

570 

526.0 

1100 

4283 

580 

516.9 

1110 

3748 

590 

508.2 

1120 

3331 

600 

499.7 

1130 

2998 

610 

491.5 

1140 

2726 

620 

483.6 

1150 

2499 

630 

475.9 

1160 

2306 

640 

468.5 

1170 

2142 

650 

461.3 

1180 

1999 

660 

454.3 

1190 

1874 

670 

447.5 

1200 

1764 

680 

440.9 

1210 

1732 

690 

434.5 

1220 

1666 

700 

428.3 

1230 

1578 

710 

422.3 

1240 

1499 

720 

416.4 

1250 

1428 

730 

410.7 

1260 

1363 

740 

405.2 

1270 

1304 

750 

399.8 

1280 

1249 

760 

394.5 

1290 

1199 

770 

389.4 

1300 

1153 

780 

384.4 

1310 

1110 

790 

379.5 

1320 

1071 

800 

374.8 

1330 

1034 

810 

370.2 

1340 

999.4 

820 

365.6 

1350 

967.2 

830 

361.2 

1360 

936.9 

840 

356.9 

1370 

908.6 

850 

352.7 

1380 

881.8 

860 

348.6 

1390 

856.6 

870 

344.6 

1400 

832.8 

880 

340.7 

1410 

810.3 

890 

336.9 

1420 

789.0 

900 

333.1 

1430 

768.8 

910 

329.5 

1440 

749.6 

920 

325.9 

1450 

731.3 

930 

322.4 

1460 

713.9 

940 

319.0 

1470 

697.3 

950 

315.6 

1480 

681.4 

960 

312.3 

1490 

666.3 

970 

309.1 

1500 

651.8 

980 

305.9 

1510 

637.9 

990 

302.8 

1520 

624.6 

1000 

299.8 

1530 

611.9 

1010 

296.9 

1540 

599.6 

1020 

293.9 

1550 

587.9 

1030 

291.1 

1560 

576.6 

1040 

288.3 

1570 

















RADIO THEORY SIMPLIFIED 


163 


Table Showing the Relation of Wave Length to Frequency—Continued 


W. L. 

Freq. 

W. L. 

Freq. 

W. L. 

Freq. 

15C0 

189.8 

2140 

140.1 

2710 

110.6 

1550 

188.6 

2150 

139.5 

2720 

110.2 

1600 

187.4 

2160 

138.8 

2730 

109.8 

1610 

186.2 

2170 

138.1 

2740 

109.4 

1620 

185.1 

2180 

137.5 

2750 

109.0 

1630 

183.9 

2190 

136.9 

2760 

108.6 

1610 

182.8 

2200 

136.3 

2770 

108.2 

1650 

181.7 

2210 

135.7 

2780 

107.8 

1660 

180.6 

2220 

135.1 

2790 

107.5 

1670 

179.5 

2230 

134.4 

2800 

107.1 

1680 

178.5 

2240 

133.8 

2810 

106.7 

1690 

177.4 

2250 

133.3 

2820 

106.3 

1700 

176.4 

2260 

132.7 

2830 

105.9 

1710 

175.3 

2270 

132.1 

2840 

105.6 

1720 

174.3 

2280 

131.5 

2850 

105.2 

1730 

173.3 

2290 

130.9 

2860 

104.8 

1732 

173.2 

2300 

130.4 

2870 

104.5 

1740 

172.3 

2310 

129.8 

2880 

104.1 

1750 

171.3 

2320 

129.2 

2890 

103.7 

1760 

170.4 

2330 

128.7 

2900 

103.4 

1770 

169.4 

2340 

128.1 

2910 

103.0 

1780 

168.4 

2350 

127.6 

2920 

102.7 

1790 

167.5 

2360 

127.0 

2930 

102.3 

1800 

166.6 

2370 

126.5 

2940 

102.0 

1810 

165.6 

2380 

126.0 

2950 

101.6 

1820 

164.7 

2390 

125.4 

2960 

101.3 

1830 

163.8 

2400 

124.9 

2970 

100.9 

1840 

162.9 

2410 

124.4 

2980 

100.6 

1850 

162.1 

2420 

123.9 

2990 

100.3 

1860 

161.2 

2430 

123.4 

3000 

99.94 

1870 

160.3 

2440 

122.9 

3020 

99.28 

1880 

159.5 

2450 

122.4 

3040 

98.62 

1890 

158.6 

2460 

121.9 

3060 

97.98 

1900 

157.8 

2470 

121.4 

3080 

97.34 

1910 

157.0 

2480 

120.9 

3100 

96.72 

1920 

156.2 

2490 

120.4 

3120 

96.10 

1930 

155.3 

2500 

119.9 

3140 

95.48 

1940 

154.5 

2510 

119.5 

3160 

94.88 

1950 

153.8 

2520 

119.0 

3180 

94.28 

1960 

153.0 

2530 

118.5 

3200 

93.69 

1970 

152.2 

2540 

118.0 

3220 

93.11 

1980 

151.4 

2550 

117.6 

3240 

92.54 

1990 

150.7 

2560 

117.1 

3260 

91.97 

2000 

149.9 

2570 

116.7 

3280 

91.41 

2010 

149.2 

2580 

116.2 

3300 

90.86 

2020 

148.4 

2590 

115.8 

3320 

90.31 

2030 

147.7 

2600 

115.3 

3340 

89.77 

2040 

147.0 

2610 

114.9 

3360 

89.23 

2050 

146.3 

2620 

114.4 

3380 

88.70 

2060 

145.5 

2630 

114.0 

3400 

88.18 

2070 

144.8 

2640 

113.6 

3420 

87.67 

2080 

144.1 

2650 

113.1 

3440 

87.16 

2090 

143.5 

2660 

112.7 

3460 

86.65 

2100 

142.8 

2670 

112.3 

3480 

86.16 

2110 

142.1 

2680 

111.9 

3500 

85.66 

2120 

141.4 

2690 

111.5 

3520 

85.18 

2130 

140.8 

2700 

111.0 

3540 

84.70 



















164 


RADIO THEORY SIMPLIFIED 


Tabic Showing the Relation of Wave Length to Frequency— Continued 


W. L. 


3560 

3580 

3600 

3620 

3640 

3660 

3680 

3700 

3720 

3740 

3760 

3780 

3800 

3820 

3840 

3860 

3880 

3900 

3920 

3940 

3960 

39*0 

4000 

4020 

4040 

4060 

4080 

4100 

4120 

4140 

4160 

4180 

4200 

4220 

4240 

4260 

4280 

4300 

4320 

4340 

4360 

4380 

4400 

4420 

4440 

4460 

4480 

4500 

4520 

4540 

4560 

4580 

4600 

4620 

4640 

4660 

4680 

4700 


Freq. 

84.22 

83.75 

83.28 

82.82 

82.37 

81.92 

81.47 
81.03 
80.60 
80. 17 

79.74 

79.32 

78.90 

78.49 
78.08 
77.67 

77.27 
76.88 

76.49 

76.10 

75.71 

75.33 

74.96 

74.58 

74.21 

73.85 

73.49 

73.13 

72.77 

72.42 
72.07 

71.73 

71.39 
71.05 

70.71 

70.38 
70.05 

69.73 

69.40 
69.08 

68.77 

68.45 

68.14 

67.83 
67.53 

67.22 

66.91 
66.63 

66.33 
66.04 

65.75 

65.46 

65.18 
64.90 
64.62 

64.34 
64.06 

63.79 


W. L. 


4720 

4740 

4760 

4780 

4800 

4820 

4840 

4860 

4880 

4900 

4920 

4940 

4960 

4980 

5000 

5050 

5100 

5150 

5200 

5250 

5300 

5350 

5400 

5450 

5476 

5500 

5550 

5600 

5650 

5700 

5750 

5800 

5850 

5900 

5950 

6000 

6050 

6100 

6150 

6200 

6250 

6300 

6350 

6400 

6450 

6500 

6550 

6600 

6650 

6700 

6750 

6800 

6850 

6900 

6950 

7000 

7050 

7100 


Freq. 

63.52 

63.25 
62.99 

62.72 

62.46 
62.20 

61.95 

61.69 

61.44 

61.19 
60.94 

60.69 

60.45 

60.20 

59.96 
59.37 

58.79 

58.22 
57.66 

57.11 

56.75 
56.04 

55.52 
55.01 

54.76 
54.51 
54.02 
53.54 
53.07 
52.60 

52.14 

51.69 

51.25 

50.82 

50.39 

49.97 

49.56 

49.15 

48.75 
48.36 

47.97 

47.59 

47.22 

46.85 

46.48 

46.13 

45.77 

45.43 
45.09 

44.75 
44.42 
44.09 

43.77 

43.45 

43.14 

42.83 

42.53 
.2342 


W. L. 


7150 

7200 

7250 

7300 

7350 

7400 

7450 

7500 

7550 

7600 

7650 

7700 

7750 

7800 

7850 

7900 

7950 

8000 

8050 

8100 

8150 

8200 

8250 

8300 

8350 

8400 

8450 

8500 

8550 

8600 

8650 

8700 

8750 

8800 

8850 

8900 

8950 

9000 

9050 

9100 

9150 

9200 

9250 

9300 

9350 

9400 

9450 

9500 

9550 

9600 

9650 

9700 

9750 

9800 

9850 

9900 

9950 

10000 


Freo. 


41.93 
41.64 

41.35 
41.07 

40.79 
40.52 

40.24 

39.98 

39.71 

39.45 

39.19 

38.94 

38.69 

38.44 

38.19 

37.95 

37.71 

37.48 

37.25 
37.02 

36.79 

36.56 
36.34 

36.12 

35.91 

35.69 

35.48 

35.27 
35.07 

34.86 
34.66 

34.46 

34.27 
34.07 
33.88 

33.69 

33.50 
33.31 

33.13 

32.95 

32.77 

32.59 

32.41 
32.24 
32.07 

31.90 

31.73 

31.56 

31.39 

31.23 
31.07 

30.91 

30.75 

30.59 

30.44 

30.28 

30.13 

29.98 




















RADIO THEORY SIMPLIFIED 


165 


form «r>a» 


Department of commerce 

BUREAU OF NAVIGATION 

RADIO SERVICE 


INTERNATIONAL RADIOTELEGRAPHIC CONVENTION 

LIST OF ABBREVIATIONS TO BE USED IN RADIO COMMUNICATION 


IBBREYl- 

ATiOil 


PRO 


QSP 


qsy 



QSZ 

QXP 


QUESTION 


Do yea to communicate by means of the 
International Signal Code? 

What ship or coast station 1 a that?........ 

What Is your distance?. ... 

What Is your true bearing!.............. 

Where are yon bound fori. 

Where are you bound from!.. 

What tine do you bclone tot.. 

What Is yoor wave length In meters!.. 

Hon many words hate yon to send). 

How do yon receive me!...... 

Are yon receiving badly I Shall 1 send 20?,, 

• • • •— • . 

for adjustment?.. 

Are yon being Interfered with?. 

Are the atmospherics strong!.. 

Shall I Increase powert.... 

Shalt I decrease power?.. 

Shall I aend faster! ... 

Shall t send slower! .. 

Shall 1 stop sending!. 

Hate you anything for me?. 

Are you ready!... 

Are you busy!. 


Shall I stand byT,. 

When will be my turn!...... 

Are my signals weak!.* 

Are my signals strong!.........* 

Is my tone bad!... 

,1s ray spark bad!.... 

la my sparing had!...... 

What Is your time!... 

la transmission to be la alternate order or In 
eeriest 


W'hat rate shall I collect for.?. 

Is the last radiogram canceled. 

Did you get my receipt!... 

What Is your true courset. 

Are yeu In communication with land!.. 

Are yon In communication with any ship or 

station (or: with...._)! 

Shall I Inform.that yon are calling 

hunt 

fs.calling me?.. 

Will yon forward the radiogram?.. 

Have you received the general call?. 

Please call me when you have finished (or: 
at.o’clock)? 

Is public correspondence being handled?..,. 

Shall I Increase my nark frequency?. . 

Shall 1 decrease my- Spark frequency?.. 

Shall I send on a wave length of.. 

meters? 


w hat i ny true bearing?. 
What Is my position? 


ANSWER OR NOTICE 


I wish to communicate by means ef the 
International signal Code. 

This Is. 

My distance Is ........ 

My true bearing is....degrees* * 

1 am bound for........ 

1 sm bound from........ 

1 belong to the.Line. 

My waveJength Is.meters* 

I nave.words to send. 

I am recetvtrfg well, 
lam receiving badly. Please send SQh 
» . • — • 
for adjustment. 

T am being Interfered with. 

Atmospherics are very strong. 

Increase power. 

Decrease power. 

Send faster. 

Send slower. 

Stop sending. 

I have nothing for yon. 

1 am ready. All right nose. 

1 am busy (or: I am busy with..,..,)* 
Please do not Interfere. 

Standby. I will call yon when required. ; 
Your turn will be No. ........ 

Your signals are weak. 

Your stcnals are strong. 

The tone Is bad. 

The spark Is bad. 

Your spacing la bad. 

My time U. 

Transmission will be la alternate ordea. 

Transmission will be In aeries of 5 message*. 
Transmission will be in series of 10 message*. 

Collect. 

The last radiogram la canceled. 

Please acknowledge. 

My true course Is...... .degrees. 

1 am not In communication with land. 

1 am In communication with.. 

(through.). 

Inform.that 1 era calling Mas. 

Yon are being called by.* 

1 will forward the radiogram. 

General call to all stations. 

YVlll call when 1 have finished. 

Public correspondence fs being handled. 

Please do not Interfere. 

Increase your spark frequency. 

Decrease your spark frequency. 

Let ns change to the wave length of. 

meters. 

Send each word twice. I have difficulty la 
receiving you. 

Repeat the last radiogram. 

Your true bearing la.degree* from ..... 

Your position la.... latitude.... longitude. 



















































































t 


t 









APPENDIX “B 








APPENDIX “B” 


THE AMATEUR RADIO OPERATOR 
AND THE A.R.R.L. 

As stated in the preface, this book was written pri¬ 
marily for the class of people known as “B.C.L’s” or 
Broad-Cast Listeners. 

It is believed that too often the B.C.L. is ready to 
criticize the amateur radio operator. It is also believed 
that if a better understanding were had between these 
two classes of radio fans, each would be more considerate 
of the rights of the other. To help make this possible, 
the author has included in this appendix, a few facts 
which he hopes, will enable the reader, who is a broad¬ 
cast listener, to better understand the aims and aspir¬ 
ations of the amateur radio operator. 

These operators are, with a few exceptions, all mem¬ 
bers of the A.R.R.L. or American Radio Relay League. 
The aims of this organization can be understood best by 
quoting from the By-Laws of the League. This quotation 
appears in every issue of their official organ, QST. 


“The American Radio Relay League, Inc. is a national 
non-commercial association of radio amateurs, bonded 
for the more effective relaying of friendly messages be¬ 
tween their stations, for legislative protection, for orderly 
operating, and for the practical improvement of short¬ 
wave two way radio telegraphic communication. It is an 


169 



170 


RADIO THEORY SIMPLIFIED 


incorporated association without capital stock, chartered 
under the laws of Connecticut. Its affairs are governed 
by a Board of Directors, elected every two years by the 
general membership. The officers are elected or appoint¬ 
ed by the Directors. The League is non-commercial and 
no one commercially engaged in the manufacture, sale, 
or rental of radio apparatus is eligible to membership on 
the Board.” 


Much of the advancement of the radio industry today 
is due to the fact that thousands of transmitting ama¬ 
teurs, scattered all over the United States, have spent 
and are still spending their time and energy in the de¬ 
velopment of the radio art. Many of the well known 
radio engineers of today were at one time transmitting 
amateurs. 

Many rules and regulations have been voluntarily ac¬ 
cepted by them, curbing their rights, in favor of the man 
who wishes to listen to a broadcast program. Of course, 
the organization, as with all organizations, has its out¬ 
laws, but it, as a whole should not be condemned because 
of the few who will not observe “silent periods.” 

It should be realized that the transmitting amateur is 
easily outnumbered by one hundred to one, and because 
of this, the higher grade amateur realizes that he must 
not infringe too greatly upon the rights of the broadcast 
listener. The broadcast listener oftentimes says he does 
not see the use of transmitting the seemingly unimpor¬ 
tant messages back and forth and the amateur operator 
does not understand the broadcast listener, who is a 
“DX” hound, and does not particularly care for the 
quality of the program he is receiving, as long as it is 
a good distance away. 

In this respect, one type of amateur is doing it for the 
same reason as the other. Both trying to get the most 


RADIO THEORY SIMPLIFIED 


171 


efficient operation out of their apparatus. This desire 
calls for constructive experimental work from both par¬ 
ties and so is worth while. 

Much can still be done by the transmitting amateur to 
eliminate interference to the B.C.L. The complete elimi¬ 
nation of the spark transmitter and adoption of C. W. 
will do much to lessen interference. Other improvements 
which can be made are the total elimination of key click, 
more careful tuning of the transmitters to the allotted 
wave length and complete observation of quiet hours. 

The broadcast listener can do his part by buying or 
building more efficient receiving equipment, whereby he 
will not be interfered with by the operator who is han¬ 
dling his station properly. When the B.C.L. is interfered 
with on the higher wave lengths, he can rest assured that 
it is not amateur interference, but is undoubtedly ship or 
commercial traffic of importance. 


APPENDIX “C 











APPENDIX “C” 


LOCATING TROUBLE 


It is assumed that most of the readers of this book, either hare 
radio sets at the present time or intend buying one in the future. 
This appendix will be devoted to the explanation of some of the most 
common ways of locating the source of trouble when a radio receiving 
set does not operate successfully. It is believed that with these helps 
most any one will be able to find the most common causes of un¬ 
successful operation. 

IF THE SET FAILS TO OPERATE AT ALL 

See if the aerial and ground are connected to their proper places. 

Phone or loud speaker may be disconnected. 

“A" and “ B” batteries may be disconnected. 

Leads from “B” battery may be reversed. Trace out and see that 
the positive side of the “B” battery is connected to the plate ter¬ 
minal of the audion bulb. 

One of the tubes in the set may be burned out or the elements of 
the tube may be touching each other. 

Check the set over and see if there are any loose connections. 

A phone condenser may be shorted. 

A transformer may be shorted or burned out. 

One of the jacks in the set may be open. This oftentimes happens. 
To find out if it is causing the trouble press down on the leaves of 
the different jacks and see if a signal can be received. 

Tubes may not be making contact in their sockets. Try pressing 
down on different tubes to see if this brings in signals. 

Phone plug may not be making proper contact in jack due to its 
not being pushed in far enough. 

Dead “B” batteries. These should be tested with a volt meter. 

Variable condenser secondary coils may be shorted. 


175 



176 


RADIO THEORY SIMPLIFIED 


IF NOISES ARE HEARD IN THE SET BUT NO 
SIGNALS GAN BE RECEIVED 

Look for poor connection to aerial and ground. 

Look for poor connection to “A" battery making filament current 
unsteady. 

Set may be in an oscillating condition due to the tickler coil being 
too closely coupled. 

Grid wire or return lead from grid to “A" battery may be open. 
This generally causes a very pronounced A-C hum or whistle. 

Variable condenser may be shorted. (Keep variable condensers 
free from dust between plates.) 

“B” battery voltage on the detector may be too high. Try chang¬ 
ing Detector “B" battery voltage. 

Jacks may be open. 

Noises may be due to power leaks, x-ray machines, motors, arc 
lights, flickering, etc. To see if this is causing trouble, disconnect 
aerial and ground to see if noises disappear. 

Lighting Arrestor may be shorted. 

WEAK SIGNALS 

Exhausted “A” or “B” battery. 

“A” battery terminals reversed. 

Poor bulbs. 

Poor socket contacts. 

Inefficient transformers. 

Amplifier “B” battery voltage too low. 

Detector “B” battery voltage too high or too low. 

Poor phones or loud talker. 

Poor grid condenser. 

Grid leak not of proper value. Try changing to different sizes. 

Phones or loud speaker leads may be reversed. Try changing 
around and see which gives best signals. 

Set may not tune to wave length which it is desired to hear. Try 
adding loading coils. 

Tickler coil connections may be reversed. 

Phone condenser omitted. 

Shellac or parrafin on coils. Use high diaelectric varnish only. 

Signals may be fading. Noticed especially in the summer time 
and on distant stations. Nothing can be done to rectify this trouble 
except that sometimes where the fading comes at long intervals 
variations may be followed by changing the tuning. 


RADIO THEORY SIMPLIFIED 


177 


Poor aerial or ground.1 Fastened ground to water pipe or to pipe 
chiven into moist earth. 

Inefficient parts used in set. 

Leads to primary of audio frequency transformer may be reversed. 

Set untuned. Some radio frequency sets are very hard to tune, 
so do not become discouraged until sure you know how to operate. 

NOISES PRESENT WITH SIGNALS 

Static, especially in summer. Not much can be done to overcome 
static, except that shorter aerials or a loop may be used. Sets using 
radio frequency amplification do not amplify static to any great 
extent. 

Power leak caused by defective transformer or poor insulator of 
high tension line. If sure this is causing trouble, notify local power 
company. 

Battery charger operating close by. 

Arc light flickering. 

Passing street cars. 

Noises caused by improperly operated nearby regenerative sets. 

One broadcasting station heterodyning another. 

If noises are caused by any of the reasons above, they should 
practically disappear when antenna and ground are disconnected. 

Noisy or nearly exhausted "B" battery. 

Excessive regeneration. 

Amplifier tubes turned up too high. 

Corroded connections caused by using acid flux in soldered joints. 

If using reflex set crystal may not be making contact. 

Radio or audio frequency transformers too close together. Spread 
apart and place at right angles to each other. 

Noises are caused by vibration of UV 199 type Bulb. Use sponge 
rubber cushioned socket. 

Leaking or broken down condensers. 

Noise can be heard if set has a loose connection, especially when 
set into vibration. 

Pencil marks or acid making low resistance path between ter¬ 
minals. 


CAUSES OF DISTORTED SIGNALS 

Defective bulbs. 

Defective transformers. 

Excessive regeneration. Loosened coupling of tickler and turned 
down detector bulb. 

Excessive “B" battery voltage. 

Overloading phones or loud speaker. 


INDEX 


Page 

ABBREVIATIONS 

Code Telegraphic.161 

International.161 

Radio.160 

Units.*.157 

ACMEDYNE CIRCUIT. 84 

AERIAL 

Capacity. 37 

Insulators. 96 

Location of. 39 

Loop.40-111 

Metal Plates used as.37 

Natural wave length of.42 

Poorly constructed.40 

Receiving.40 

Transmitting. 38 

Tuning. 41-42-43 

Wire.96 

ALTERNATING CURRENT 

Compared with direct current.25 

Wave form. 25 

Amateur Wireless Operator.169 

A. R. R. L. American Radio Relay League.169 

AMMETER 

Use of. 20 

AMPERE 

Explanation of. 19 

AMPERE HOUR 

Capacity of battery. 95 

AMPLIFICATION 

Theory of Audio Frequency. 56 

Theory of^ Radio Frequency.59 

Regenerative. 64 


178 





























AMPLIFIER 

Audio. 81 

Power. 92 

Radio. 90 

Tube..*128 

AMPLITUDE 

Change in modulated wave. 23 

Of damped wave. 22 

Of undamped wave. 21 

ANTENNA 
See aerial 

APPARATUS 

Receiving. 94 

Symbols for.158 

ATOM 

Composition of.48 

AUDIO FREQUENCY 

Amplifier. 81 

Transformers.121 

AUDION BULB 

Amplifier. 56 

Detector or Rectifier.49 

Three Element.50 

Two Element.49 

UV 199 or C 299.126 

UV 201 or C 300.128 

UV 201 A or C 301 A.128 

WD 11 or C 11.130 

WD 12or C 12.131 

Northern Electric 215-A.133 

Western Electric 216-A.135 

BATTERIES 

“A” Dry. 95 

“A” Storage. 94 

“B” Dry.97 

“B” Storage. 98 

"C” Use of.101 

BATTERY 

Charger. 99 

BROWN AND SHARP 

Wire Gauge.159 

BULB 

See Audion Bulb 


179 
































Page 

BY PASS 

Condenser. 46 

"C”BATTERY 
See batteries 

CAPACITY 

Antenna.37-39 

Of Batteries. 94 

Of Condensers.101 

Unit of Measurement.101 


CARRIER WAVE 

See modulated wave 

CASCADE AMPLIFICATION 

See audio and radio frequency Amplification 


CHOKE COILS 

Where used.101 

CIRCUITS 

Use of. 62 

Acmedyne. 87 

Amplifier Audio.81-57 

Amplifier Radio.90-59 

Armstrong original regenerative. 64 

Crystal Detector. 67 

Inverse Duplex. 86 

Neutrodyne. 78 

Reflex. 80 

Reinartz. 77 

Single Non-Regenerative. 70 

Single Regenerative. 72 

Super Heterodyne. 82 

Three circuit Regenerative. 75 

Two Circuit Non-Regenerative. 70 

CLOSE COUPLING. 78 

CODE 

International Telegraphic.165 

COIL ANTENNA 
See Loop 
CONDENSER 

Antenna. 41 

By-pass.46-101 

Fixed.101 

Grid.54-105 

Phone, same as by-pass 

Shunt. 43 

Tuning by means of.43 

Variable.102 




180 
































CONDUCTORS 

Good and poor.48 

CONTINENTAL 

Wireless Code.165 

CONTINUOUS WAVES 
See undamped waves 

COPPER CLAD WIRE. 96 

COPPER WIRE TABLES.159 

COUNTERPOISE. 39 

COUPLING 

Of tuning coils.44 

CRYSTAL DETECTOR 

Circuits.67-68 

Rectification of.45 

Reflex Circuits.80 

Types of.103 

CURRENT 

In aerial.33-34 

Alternating. 25 

Direct. ; .... 24 

Measuring instruments. 20 

Pulsating direct. 33 

Thru vacuum tubes. 51 

Unit of measuring.19-20 

60 Cycle. 34 

CYCLE 

See frequency 

DAMPED WAVES.31 

DETECTOR 

Audion Bulb.50 

Crystal.46 

DIELECTRIC MATERIALS.47 

DIRECT CURRENT. 24 

DISTORTION OF SIGNALS.Appendix “C” 

ELECTRIC CURRENT See current 

ELECTRICAL PRESSURE OR VOLTAGE.19-20 

ELECTRON 

Flow.48 

Theory. 47 

Tube, see vacuum tube 

ELECTROLYTE IN STORAGE BATTERIES.108 

E. M. F. or ELECTROMOTIVE FORCE. 20 

181 


r 































Pa«e 


FILAMENT 

Current, regulation.50-117 

In vacuum tube.49-50 

Rheostat.....117 

FIXED CONDENSERS See condensers 

FLEMING VALVE 

See audion bulb, two element 

FREQUENCY 

Of radio waves.26-28 

Of Audio waves.57-58-30 

GALANA AS DETECTOR. 46 

GAUGE 

See wire gauge 

GRID 

Battery see “C” battery 

Characteristics in vacuum tube. 50 

Condenser.54-105 

Current. 54 

Leak.54-105 

GROUND 

Clamp.106 

Use of.38-39 

Good Ground for Radio.>.106 

HONEYCOMB COIL.107 

HOOK-UPS See Circuits 

HYDROMETER.108 

INDUCTANCE.71-40 

INSULATION. 47 

INSULATORS, AERIAL. 96 

INTERFERENCE.32-65 

INTERNATIONAL Telegraphic Code.165 

LEAK GRID.54-105 

LOOPS.Ill 

LOOSE COUPLERS.110 

LOOSE COUPLER CIRCUITS.71-69 

LOUD SPEAKERS.112 

METER Unit of measurement.26 

MICROFARAD.101 

MODULATED WAVE.53 

MODULATING ACTION.33 

NEGATIVELY CHARGED BODIES.47 


182 
































OHMS LAW. 

OPERATOR, LICENSED AMATEUR.. 
OSCILLATIONS 

Damped. 

Undamped. 

OSCILLATING CURRENTS. 

PANCAKE COIL See Spiderweb Coil 

PHONE CONDENSER. 

PLATE 

In audion bulb. 

Circuit tuned. 

Milliammeter. 

Voltage of audion bulbs. 

POTENTIOMETER. 

POWER 

Amplifier. 

Tube. 

PRIMARY CIRCUIT TUNING 
RADIO 

Frequency Amplification. 

£ Telephone—how made possible. 

> Waves. 

Wave-train. 

RECEIVING SETS See Chapter V 
REGENERATION 

How obtained. 

Theory of. 

REGENERATIVE SETS. 

RE-RADIATION OF RECEIVING SET 
RESISTANCE 

In wire... 

Units. 

RHEOSTAT 

Filament. 

SATURATION POINT OF BULB. 

SECONDARY CIRCUIT. 

SOLDERED CONNECTIONS 

Care in making. 

SPARK TRANSMITTING SETS. 

SPEED OF RADIO WAVE. 

SPEED Of SOUND WAVE. 


P 


19 


Appendix “B" 


31 

29 

30 


....101 

.... 49 
.... 75 
.... 48 
126-136 

....115 

.... 92 
....135 


.. 59 
.. 51 
21-22 
,. 22 


.64 

.64 

.72-78 

.65 

.47-159 

.....116 

.117 

.55 

.44-76 

Appendix “C” 

.32 

.26 

.29 


183 
































Page 

SOUND WAVES. 29 

STATIC.Appendix “C" 

STORAGE BATTERY. 94 

SUPERHETERODYNE. 82 

TAPPED COILS. 42 

TESTING FOR TROUBLE IN RECEIVING SET. Appendix “C” 

THERMONIC VALUE See audion bulb 

TRANSFORMERS 

Audio.121 

Radio.123 

Why used. 57 

TRANSMITTING STATIONS.32 

TROUBLE FINDING.Appendix “C” 

TUNED PLATE. 75 

TUNING 

Antenna. 41 

Primary. 41 

Radio Frequency Transformers.90 

Secondary.69-71-7 6 

UNDAMPED WAVES. 29 


VACUUM TUBES See audion bulbs 

VARIABLE CONDENSERS.102 

VARIABLE RESISTANCE.115-117-116 

VARIO COUPLER.124 

VARIOMETER.124 

VOLT. 20 

VOLTAGE DROP IN D. C. CURRENT. 20 

WATER ANALOGY.19-20-50 


WAVES 

Amplitude of. 21 

Carrier. 33 

Damped. 31 

Length, how measured. 21 

Light. 22 

Modulated Sound. 29 

Train.22-53 

Undamped. 29 


WEIGHT OF ELECTRON.47 

WIRE 

Antenna. 96 

Gauge.159 

ZERO BEAT RECEPTION. 94 

ZINITE MINERAL.103 


184 






































PART II 


A RADIO DICTIONARY 
OF RADIO TERMS 
AND WORDS 















V 


Radio Dictionary 


Absorption Modulation—Process of varying the amplitude of a high 
frequency alternating current in accordance with a desired wave 
form by a systematic absorption of energy from the circuit in a 
part of the circuit which serves as an appropriate variable resistance. 

Acceptor —A combination of capacity and inductance attuned to the 
frequency of a desired signal, and connected in series with the aerial. 

Aerial Wire —See Antenna. 

Air Condenser—One having air as the dielectric, with the support made 
of a minimum of solid dielectric. 

Alternating Current Characteristic—The relation indicated by a graph 
using the impressed E. M. F. as abscissas and the resultant current 
ns ordinates for alternating E. M. F. and current. (See Alternating 
Current). 

Alternating Current, Damped —See Damped Alternating Current. 

Alternating Current, Forced —See Forced Alternating Current. 

Alternating Current, Free —See Free Alternating Current. 

Alternating Current, Undamped —See Undamped Alternating Current. 

Alexanderson Alternator—An alternator of the inductive type which 
directly generates currents of sufficiently high frequency to be 
used in Radio Telegraphy. 

Alternating Current—A current that periodically reverses its direction. 

Alternation—One half cycle or the rise and fall of a current in one 
direction. 

Alternator—A generator for producing alternating currents. 

Amateur Call Letters—Certain combinations of letters that are assigned 
to amateur radio stations for purposes of identification. 


187 



188 


RADIO THEORY SIMPLIFIED 


Amatear Publications—Books and magazines that are published for the 
use of Amateur Radio Operators 

Amateur Station License—The permit issued by the government to 
amateur radio operators owning transmitting sets. 

American Wire Gauge—The arbitrary series of numbers assigned to 
wires to indicate their sizes. 

Ammeter—An instrument for measuring electric current intensity in 
a circuit in Amperes. 

Ampere—The standard electrical unit of current. This is the current 
flowing in a circuit of one ohm resistance under a pressure of one 
volt. 

Ampere-Hour—Unit for expressing the quantity of electricity passing 
in a circuit. This is a current of one ampere flowing for one hour. 

Amplification Factor—The ratio between the plate voltage and grid 
voltage for constant plate current. 

Amplifier—A device or arrangement to augment or strengthen feeble 
oscillations (either of audio or radio frequency). 

Amplitude—The measure of the maximum deviation of an electric wave 
from its zero point. 

Antenna—A conductor designed for absorbing or radiating the energy 
of radio waves. 

Antenna Resistance—The opposition offered to ‘‘he electric current by 
the electrical properties of the antenna. See Radiation Resistance. 

Antenna, Effective Resistance of—The quotient of the power given to the 
antenna by the square of the antenna current. 

Arc Converter—An electric arc used for the conversion of direct to 
alternating or pulsating current. 

Arc—The completion of an electric circuit through a gas or vapor, 
the conductivity of which is due to the ionization of that gas or 
vapor. Used as a source of undamped oscillation. 

Armature Core—The iron mass which supports the armature winding. 

Armature Winding—The conductors in which an electric current is in¬ 
duced by the action of the electromagnetic field in an electric 
machine. 

Atom—The particle or particles that go to make up molecules. The 
smallest particle of matter that can enter into combination. 


RADIO THEORY SIMPLIFIED 


189 


Atmospheric Absorption—The part of the total loss of energy by 
atmospheric conductivity, reflection and refraction. 

Attenuation—The decrease, with distance from the source, of the magni¬ 
tude of amplitude, of any electric or magnetic wave. 

Audibility—The ratio of the current producing a signal in the receivers 
to the current producing a barely audible signal. 

Audion—See Electron Tube. 

Autodyne Reception—See Self-Heterodyne. 

Audio Frequency—A frequency capable of producing sound in the human 
ear. Considered to be below ten thousand cycles per second. 


B 


“B" Battery—A battery used as the source of current in the plate 
circuit of a vacuum tube. 

Bakelite —A high grade and efficient insulating material of the phenolic 
group. 

Band, Wave Length—The “side waves” due to the varying amplitude 
and frequencies of the modulating wave. 

Beat Frequency—The frequency of recurrence of maxima of addition 
or minima of opposition of two superposed periodic phenomena 
of the same kind but of different frequencies. 

Beat Reception—The resultant audible frequency when two sources of 
unequal undamped electrical oscillations of constant amplitude act 
simultaneously in the same circuit. 

Biasing Potential—The potential impressed on the grid of a vacuum 
tube to cause it to operate at the most desirable part of its character¬ 
istic curve. 

Broadcast —Organized one way transmission of news, music or other matter 
interesting to the public. See Radiocast. 

Buzzer —An electromagnetic device with a vibrating member opening and 
closing its own circuit. 

Buzzer Modulation—A process for varying the output power of a con¬ 
tinuous wave generator at the tonal frequency of the buzzer used. 

By-Pass Condenser—A fixed capacity offering a high impedance to currents 
of low frequency but lower impedance to radio frequency currents. 


190 


RADIO THEORY SIMPLIFIED 


C 


“C” Battery—A source of lo\r potential used in the grid circuit of a 
vacuum tube to cause operation to take place at a particular point 
on the characteristic curve. 

Cadmium Cell—A source of E. M. F. of constant and standard value. 
A cell using cadmium as the negative electrode. 

Cage Antenna—One having conductors arranged cylindrically. 

Call Letters—Certain combinations of letters assigned to radio stations 
by the government. The group of letters assigned the U. S. by 
the International Radiotelegraph Convention are all three and four 
letter combinations beginning with N and all beginning with W and 
all combinations of KDA to KZZ inclusive. 

Capacity—The measure of the amount of electrical energy a condenser 
can store up, the unit being the farad. 

Capacitance—See Capacity. 

Capacitive Coupling—The coupling of one circuit to another whereby the 
energy transfer is by means of condenser action. 

Capacity Resistance—The opposition offered to an alternating current by 
a condenser. 

Carrier Wave—The principal radio frequency wave providing the means 
for carrying the modulated or audio frequency wave. 

Carborundum—A synthetic crystalline material (silicon carbide) used as 
a detector. 

Carbon Rheostat—A rheostat using carbon as the resistance material. 

Cascade Amplification—The method of successively using two or more 
vacuum tubes for amplification. 

Centimeter—Metric measure of length. (One Hundredth of a meter). 

Central Station, Radio—Combined multiplex transmitting station and 
multiplex receiving station simultaneously operating several radio 
channels. 

Chemical Rectifier—A chemical device for changing alternating current to 
pulsating direct, usually used for storage battery charging. 

Circular Mil—The square of the diameter of a wire in mils. The measure 
of sectional area of a wire. 


RADIO THEORY SIMPLIFIED 


191 


Coil Antenna—One consisting of one or more complete turns of wire. 
(See Loop Antenna). 

Condenser Antenna—An antenna consisting of two capacity areas. 

Coupling Coefficient—The ratio of the mutual impedance component of 
two circuits to the square root of the product of the total impedance 
components of the same kind in the two circuits. 

Choke Coil—A coil so wound as to offer a choking or self inductance 
effect to an alternating current. 

Chopper—A device for rapidly opening and cltsing a circuit. 

Circuit—A path through which an electric current may be established. 

Circuit breaker—A special type of switch arranged to open a circuit when 
overloaded without injury to itself. 

Close Coupling—The condition in which two coils are placed in close mag¬ 
netic proximity to each other, thus establishing mutual induction. 

Closed Core—A core in which the magnetic path of iron is unbroken. 

Coated Filament—The coating of oxide on a vacuum tube filament for 
greater electron emission and longer life. 

Code—The system of dots and dashes used to represent the letters of the 
alphabet, numerals, and other symbols. 

Collector Ring—Metallic rings in contact with brushes for completing the 
circuit to a rotating member. 

Commutator—A device used on a dynamo to reverse the connection pe¬ 
riodically in order to cause the current to flow in one direction, i. e., 
to produce direct current. 

Condenser—A device for storing up electrical energy and consisting of 
two conducting surfaces or electrodes separated by an insulating 
medium called a dielectric. 

Conductance—The reciprocal of resistance; i. e., a measure of the ease 
with which an electric current will flow through a circuit. 

Conducting Materials—Those substances which offer relatively little resist¬ 
ance to the passage of an electric current. 

Conductivity—The measure of the current carrying power of a substance. 
The reciprocal of specific resistance. 

Conductor—A substance which offers a relatively small opposition to the 
passage of an electric current. 

Continuous Waves—A series of waves or cycles of current all of which 
have a constant or unvarying amplitude. 

Counter Electromotive Force—An E. M. F. that opposes the E. M. F. 
causing it. 


192 


RADIO THEORY SIMPLIFIED 


Conlomb—The quantity of electricity transferred by a current of one 
ampere in one second. 

Counterpoise—A system of electrical conductors used to complete the 
antenna capacity effect in place of the usual ground connection. 

Coupler—A device for the transfer of the energy of radio oscillations 
from one circuit tb another. 

Crystal Detector—A form of detector making use of the contact between 
a metal point and any one of certain metallic crystals, or using 
two crystals for the detector action. 

Current—A flow of electricity manifesting its presence by the magnetic 
or heating effects it produces. The unit of current is the Ampere and 
is the rate of flow in a circuit of one ohm resistance under a potential 
of one volt. 

Curve, Sine—A curve in which the ordinate varies in length according to 
the sine of the angle of its progression. A curve representing graph¬ 
ically the alternating current. 

Curve Resonance—The graphical representation of the changes of current 
in a circuit. 

Cycle—One complete set of one positive and one negative alternation of 
current. 


D 


Damped Wave—A wave consisting of a series of oscillations or cycles of 
current of gradually decreasing amplitude. 

Damping—The decreasing of the amplitude of oscillations caused by re¬ 
sistance in the circuit. 

Damping Factor—The product of the logarithmic decrement and the fre¬ 
quency of a logarithmically damped alternating current. 

Decrement—A number indicating or bearing a relation to the rate of 
decrease of amplitude in a wave train. 

Decremeter—An instrument for measuring the logarithmic decrement of 
a circuit. 

Detector—A device which converts or rectifies high frequency oscillations 
into a pulsating direct current or which translates radio frequency 
power into a form suitable for the operation of an indicator. 


RADIO THEORY SIMPLIFIED 


193 


Detector Coefficient—A measure of the curvature of the plate current 
grid-voltage characteristic of a three electrode tube. 

Diaphragm—The vibrating disc in a receiver which gives an audible sound 
under the influence of an electric current. 

Dielectric—An insulating, substance which allows electrostatic induction 
to act across it, as in the insulating medium between the plates 
of a condenser. 

Dielectric Absorption—The penetration of a dielectric by the electric 
strain during a period of time. 

Dielectric Strength—The property of a material which resists the passage 
of an electric current. It is measured in terms of volts required 
to break down this resistance. 

Dielectric Constant—The ratio of the capacity of a condenser with a 
given dielectric to the capacity of the same condenser with air as 
the dielectric. 

Direct Coupling—Association of two radio circuits by having a condenser, 
a resistor, or an inductor common to both circuits. 

Direct Current—A flow of electricity always in the same direction. 

Directional Antenna—An antenna which impels electric waves with more 
energy in one direction than in another. 

Distributed Capacity—Refers to the capacity in a coil due to the proxi¬ 
mity of the turns. 

Down Lead—See Lead-In. 

Dry Cell—A type of primary cell in which the electrolyte is in the form 
of a paste. 

Duplex Reception—The simultaneous reception of two series of signals 
by a single receiving station. 

Duplex Signaling—The simultaneous transmission and reception of sig¬ 
nals in both directions between two stations. 

Duplex Transmission—The simultaneous transmission of two series of 
signals by a single operating station. 

Dynamo—An electrical machine which gives a direct current. 

Dynamotor—A direct current machine having two windings on its ar¬ 
mature: one acting as a motor, the other as a generator. 

Dynatron—A three electrode vacuum tube which depends for its action 
on the release of electrons from an anode by electron bombardment. 


RADIO THEORY SIMPLIFIED 


1§4 


E 


Eddy Current Losses—Losses in electrical devices using iron, due to the 
currents set up in it by magnetic action. 

Edison Battery—A type of storage battery in which the elements are 
nickel and iron and the electrolyte is potassium hydroxide. 

Edison Effect—The phenomenon attributed to Edison, that when a fila¬ 
ment is incandescent a current will flow between it and another 
electrode in the tube. 

Electric Filter—See Filter. 

Electrolyte—A chemical solution used in batteries and chemical recti¬ 
fiers. 

Electrolytic Rectifier—See Chemical Rectifier. 

Electrical Oscillation—A complete cycle of high frequency current. 

Electromagnetic Lines of Force—The lines of force existing about an 
electromagnet and a current carrying conductor. 

Electromagnetic Wave—The electric wave propagated by an electrosta¬ 
tic and magnetic field intensity. Its velocity is 186,300 miles per 
second. 

Electromotive Force—The voltage or electric pressure that causes electric¬ 
ity to flow in a circuit. 

Electron—The smallest known part of matter and assumed to be a par¬ 
ticle or charge of negative electricity. 

Electron Tube—A device whose operation depends primarily upon the flow 
of electrons from one element to another. 

Electron Tube Rectifier—A device for rectifying an alternating current 
by utilizing the flow of electrons between a hot cathode and a 
relatively cold anode. 

Electrose—An insulating material. 

Electrostatic Charge—An electric charge at rest 

Electrostatic Coupling—See Capacitive Coupling. 

E. M. F.—See Electromotive Force. 

Emission of Electrons—The freeing of particles or negative charges of 
electricity from metals whose temperature is raised above red heat 

Enameled Wire—Wire which has a covering of enamel for insulating 
purposes. 


RADIO THEORY SIMPLIFIED 


195 


Energy, Conservation of—The law states that energy can neither be 
created nor destroyed. 

Equivalent Decrement—One of several quantities used as a measure 
of the distribution of the radiated power or wave amplitude with 
respect to frequency. 

Ether—The medium which permeates all space and matter and which 
transmits all electromagnetic waves. 

Exciter—A small dynamo used to excite the field coils of a larger and 
alternating current machine. 

Expansion Type Ammeter—A current measuring device which operates 
by the expansion of a metal by the heating effect of the current. 


F 


Fading—The variation of the strength of received radio signals over 
temporary periods. 

Fan Antenna—An aerial consisting of a number of wires radiating 
upwards from a common terminal to points on a supporting wire. 

Farad—The practical unit of capacity. A potential difference of one 
volt which causes a condenser to have a charge of one coulomb. 

Feed Back—The coupling of the plate circuit back to the grid circuit 
of a vacuum tube so that there is induced in the grid circuit a larger 
voltage than that originally acting. 

Feed-Voltage Modulation—The process or varying the amplitude of a 
radio frequency alternating current in accordance with any desired 
wave form by introducing additional power into the circuit of the 
high frequency generator according to the desired wave form varia¬ 
tions. 

Ferron—Iron pyrite crystals used for detector purposes. 

Ferromagnetic Modulation—A system of using the hysterectic energy 
absorption of iron or the variation of the inductance of iron core 
coils to vary the amplitude of a radio frequency current in accord¬ 
ance with a desired form. 

Fibre—An insulating material. 

Field—The name given to that part of an electrical system in which 
an electromagnetic field effect is established. 


196 


RADIO THEORY SIMPLIFIED 


Field Rheostat—A variable resistance used in the field circuit of a gener¬ 
ator or motor to control the field current and consequently the 
strength of the electromagnetic field. 

Filament—An electrically heated wire in an evacuated glass bulb form¬ 
ing one element of a vacuum tube. 

Filament Supply—A source of low potential used to send a current 
through a filament to heat it. 

Filter—A combination of inductance and capacity arranged so as to 
eliminate undesirable signals from a receiving circuit. 

Fire Underwriters—The rules for the safe installation of electrical mater¬ 
ial as set down by the National Board of Fire Underwriters. 

Fixed Condensers—One whose plates are stationary and whose capacity 
cannot be changed. 

Flat Top Antenna—An aerial consisting of parallel horizontal wires 
supported between masts. The “T" type and the inverted “L” type 
belong in this class. 

Fleming Valve—A two element electron or vacuum tube. 

Flow of Electrons—The basis for the “Edison Effect.” The passage of 
electricity from a heated filament to a plate in a vacuum tube 
where the flow consists of negative charges of electricity or electrons. 

Flux—The electromagnetic lines of force produced by a current in a 
wire or coil. 

Forced Alternating Current—One having a frequency and wave form 
which are equal to the frequency and wave form of the impressed 
electromotive force. 

Form Factor—The ratio of the effective to the average value of an alter¬ 
nating electromotive force or current. 

Free Oscillations—The alternate flow of electricity around a circuit 
first in one direction and then in the other when no outside source 
of E. M. F. is acting in the circuit. 

Frequency—The number of complete cycles of current occurring in one 
second. 

Frequency Changer—A device which delivers alternating current at a 
frequency different from the frequency of the supply current. 

Frequency Transformer—See Frequency Changer. 

Frictional Electricity—Static electricity produced by friction. 

Full Wave Rectifier—A rectifier to rectify and render available all suc¬ 
cessive half cycles of an alternating current. 


RADIO THEORY SIMPLIFIED 


197 


Fundamental—The wave length corresponding to the lowest frequency 
of free alternating current. 

Fundamental of an Antenna—The lowest frequency of free alternating 
current in an unloaded antenna. 

Fuse—An element of a circuit designed to melt or fuse at a predeter¬ 
mined value of current and used to protect the circuit from the 
destroying effects of excessive current. 


G 

Galena—A natural crystalline structure of lead sulphide used as a de¬ 
tector. 

Galvanometer—A delicate instrument used for measuring minute currents. 

Gap—An open space in a circuit through which a condenser discharges 
for producing electric oscillations. 

Gaseous Conductors—The gases which, when ionized by an electric field, 
permit the passage of an electric current. 

Gauge Wire—The method of specifying the size of wire. The two im¬ 
portant American gauges are the American Wire Gauge (Brown and 
Sharpe) and the Steel Wire Gauge. 

Gauss—The unit of magnetic field intensity measured by the force per 
unit pole or in terms of the lines of force per square centimeter. 

Geometrical Capacity—The ratio of the free charge of a condenser to 
the voltage across its terminals. 

General Call—The letter CQ in the international code and used as a 
general inquiry call. 

German Silver—An alloy consisting of nickel, copper, and zinc and used 
as a resistance material. 

Goldschmidt Alternator—A generator of high frequency currents for 
radio transmission. 

Government Radio Publications—Publications on radio subjects by the 
Bureau of Standards and Signal Corps and sold by the superin¬ 
tendent of Documents, Government Printing Office, Washington, 
D. C. 

Gram—Metric unit of weight, equivalent to 15.432 grains. 

Gram Calorie—The amount of heat required to raise the temperature of 
one gram of water one degree Centigrade. 


198 


RADIO THEORY SIMPLIFIED 


Gravity Cell—A closed circuit cell used where a continuous flow of 
current is desired. This type consists of copper and zinc electrodes 
with copper sulphate and zinc sulphate electrolyte. 

Grid—That element in a vacuum tube having the appearance of a grid 
and which controls the flow of electrons away from the filament. 

Grid Battery—The battery which is sometimes connected in the grid 
circuit of a three element electron tube to control the plate current. 

Grid Condenser—The condenser connected so as to give its charge to the 
grid in an electron tube. 

Grid Leak—The high resistance sometimes connected from the grid 
to the filament of a three electrode tube, with a condenser, to 
maintain the potential of the grid at a certain average negative 
value. 

Grid Voltage—See Grid Battery. 

Ground—An electrical connection with earth. 

Ground Lead—The conductor leading to the ground. 

Group Frequency—Often termed “Bpark frequency.” The number of 
trains of damped waves per second. 

Guy Wire—A wire used to support a radio mast. 


H 


Hard Rubber—An insulating material having a dielectric constant of 
from two to four. 

Hard Tubes—Vacuum tubes having a high vacuum. Usually of the am¬ 
plifier type. 

Harmonics—A frequency which is an exact multiple of a fundamental. 

Harp Antenna—See Fan Antenna. 

Heat—Electromagnetic wares of a frequency between that of light waves 
and radio waves. A form of energy. 

Heat Losses—Loss of energy due to the heating effect of an electric 
current. 

Henry—The inductance in a circuit in which the electromotive force in¬ 
duced is one volt when the inducing current varies at the rate of 
one ampere per second. 

Hertzian Wave—A name sometimes given to electromagnetic waves. 

Heterodyne Action—See Beat Reception. 


RADIO THEORY SIMPLIFIED 


199 


High Frequency Alternator—An alternating current generator designed 
to produce current at a high frequency. 

High Voltage—Potential of a high value. 

Honeycomb Inductance Coil—A type of coil in which the turns do not 
lie adjacent to each other but is lattice-like in appearance. 

Horsepower—A unit of power equivalent to 550 foot pounds per second 
or to 746 watts. 

Horse Shoe Magnet—A magnet which has the shape of a horse shoe. 

Hot Wire Ammeter—See Expansion Type Ammeter. 

Hydrogen—A gaseous element having a density of .00008952289 gram per 
centimeter at 0° c. and pressure of one atmosphere. 

Hydrometer—An instrument for determining the density of liquids. 


I 


Ignition Key—A rod arranged to strike the arc in an arc generator of 
high frequency currents. 

Impact Excitation—The method of transferring the electric energy in 
the primary circuit to its secondary in such a way that the secondary 
will vibrate at its own period without reaction from the primary. 
This is brought about by using an aperiodic primary circuit (see 
Aperiodic Circuit) and by the use of the quenched gap. 

Impedance—The total opposition of a circuit to the passage of an alter¬ 
nating current. 

Inclined Coil Instrument—A type of instrument in which an element, 
or elements, are inclined. 

Inductance—The property of a circuit which allows it to store up elee- 
trical energy in electromagnetic form. 

Induction—See Inductance. 

Induction Coil—A coil having a high turn ratio used for raising the 
voltage. A step-up transformer. 

Inductive Coupling—The coupling of one circuit to another whereby the 
energy transfer is by means of induction. (See Capacitive Coupling 
and Coupler). 

Inductively Coupled Receiver—A radio receiver in which the energy in 
the antenna circuit is transferred to the secondary circuit by in¬ 
duction. 


200 


RADIO THEORY SIMPLIFIED 


Inductivity—A term sometimes used to denote the dielectric constant oi 
the specific inductive capacity. 

Inductor Alternator—A type of generator for producing continuous high 
frequency currents. 

Input Circuit—Refers to the grid circuit of an electron tube. 

Inspector, Radio—The United States is divided into nine radio districts 
in each of which there is a Radio Inspector who issues licenses and 
takes charge of other radio matters under direction of the Depart¬ 
ment of Commerce. 

Insulated Wire—Wire which has a non-conducting covering. 

Insulating Materials—Those substances which oppose the passage of an 
electric current through them. 

Insulation—The material used for insulation purposes. 

Interference—The interruption to radio receiving from sources such as 
other transmitting stations, static, etc. 

Internal Drop—That part of the E. M. F. generated that is expended 
in the generator. 

International Ampere—The current which will deposit 0.001118 gram 
per sec. of silver from a neutral solution of silver nitrate. 

Interrupter—A device so arranged as to rapidly make and break a circuit. 
(See Chopper). 

Interrupted Continuous Wave—The name applied to a continuous wave 
which is interrupted, as by a chopper, before it is sent out. It 
consists of a series of wave trains, each cycle, however, having the 
same current amplitude. (Abbreviation—I. C. W.). 

Internal Output Resistance—The resistance to small alternating currents 
which exists between the plate and the filament in a vacuum tube. 

Invar—A special alloy used for standard resistance units. 

Ionic Tube—See Electron Tube. 

Ionization—The process of breaking up molecules into positively and 
negatively charged carriers of electricity called ions. 

Ion—A neutral atom or molecule to which has been added an electron 
or from which an electron has been taken. 


J 

Jamming—Transmission of waves of high decrement, that is, highly in¬ 
terfering waves. 


RADIO THEORY SIMPLIFIED 


201 


Joule—The unit of work or energy. The energy expended when a current 
of one ampere flows through a resistance of one ohm for one second. 

Joule*s Law—The heat produced in a circuit in joules is proportional to 
the resistance, to the square of the current and to the time. 


K 


Key—A special form of switch arranged for rapid operation to form 
dots and dashes of the telegraph code. 

Keying Flicker—The flickering of lights connected to the same circuit 
from which a radio transformer is operating. 

Key Click—Interfering radio frequency waves caused by opening and 
closing the circuit of a C. W. Transmitter. 

Kick Back—The passage of radio frequency currents back into the low 
frequency side of the circuit with consequent burn out of transformer 
or other apparatus. 

Kilovolt-Ampere—The unit used in rating alternating current geneiators, 
being product of kilowats and amperes. 

Kilowatt—One thousand watts. 

Kinetic Energy—The energy in a moving body. Stated in the form 
of a rule: Kinetic Energy is one half the product of the mass of 
a body by the square of its velocity. 


L 


“L” Type Antenna—See Inverted “L” Antenna. 

Lafayette Station—The arc station of 100 K. W. capacity at Bordeaux, 
France. 

Lagging Current—The phase difference in an inductive alternating current 
circuit where the current does not reach maximum until after the 
E. M. F. 

Lambda—The Greek letter used as a symbol for wave length. 

Laminations—Thin sheets of steel used as the magnetic core in electri¬ 
cal apparatus. 


202 


RADIO THEORY SIMPLIFIED 


Lattice Wound Coil—See Honeycomb Coil. 

Latour Alternator—An alternating current machine giving high fre- 
Quenciee for radio transmission. 

Laws, Radio—Regulations under which radio communication is carried 
on. 

Lead-In—The conductor from the antenna to the instruments. 

Leading Current—The phase difference in a capacitive alternating current 
where the current leads the E. M. F. 

Lead Storage Battery—A secondary battery in which the plates are 
of lead and lead peroxide and the electrolyte of dilute sulphuric acid. 

Leak, Grid—See Grid Leak. 

Leakage Current—The small current which is lost through insulators 
under certain circumstances. 

Left Hand Rule—A rule for indicating the direction of motion due to 
a force acting on a wire, when a current flows in the wire which is 
at right angles to a magnetic field. Extend the forefinger of the 
left hand in the direction of the magnetic field and hold the middle 
finger at right angles to it in the direction of the current. The 
extended thumb, held at right angles to both the other directions, 
indicates the direction of the motion. 

Length, Standards—Certain practically unvarying representations of units 
of length kept for the purpose of comparison in the Bureau of 
Standards. 

Lena’s Law—Whenever an induced current arises, by reason of some 
change in linkings, the magnetic field about the induced current 
is in such a direction as to oppose the change. 

Leyden Jar—A type of condenser jar having a metallic coating inside 
and out but not connected. (See Condenser). 

License—The law provides that in order to operate a radio transmitting 
station, both a station license and an operator’s license must be se¬ 
cured. (See Inspector, Radio). 

Light—A manifestation of electromagnetic waves ordinarily applied to 
those having a wave length of from .000075 cm. to .000038 cm. for 
the red ray to the violet ray respectively. 

Lightning—The discharge of atmospheric electricity, causing what is 
commonly called “static” in radio receivers. 

limited Commercial Stations—One of the eight classes of land radio 
stations for which provision is made in the law. 

Line Drop—That part of the E. M. F. which is expended in sending 
current through the line. 


RADIO THEORY SIMPLIFIED 


203 


Lines of Force—The directional Lines of magnetic or static field which 

represent the stresses. 

■ 

Linkage—The interlinking of the line of magnetic flux with the wire 
turns. 

Liter—A metric measure of volume equivalent to 2.113 American pints. 

Litz Wire—See Litzendraht. 

Litzendraht—A conductor consisting of several insulated wires woven 
so that they form a single conductor of low resistance to high fre¬ 
quency alternating currents. Commonly known as Litz. 

Load Flicker—The flickering of electric lights on lines supplying radio 
transmitting sets, due to the varying load. (See Keying Flicker). 

Loading Coil—The inductance coil added to radio circuits to increase their 
wave length. 

Local Action—The wasting of the zinc in primary batteries due to the 
action between the zinc and impurities in it. 

Logarithmic Decrement—The Naperian or natural logarithm of the ratio 
of two successive current amplitudes in the same direction. It may 
be considered as a constant of a simple radio circuit, being 3.1416 
times the product of the resistance by the square root of the ratio 
of the capacity to the inductance of the circuit. 

Loop Antenna—An antenna consisting of one or more complete turns of 
wire. 

Loose Coupling—The interlinking of only a small part of the flux set 
up by one coil with another coil. 

Loud Speaker—An assembly of devices by means of which received Bounds 
are made audible without the use of telephone receivers held to the 
ears. 



Magnetism—The manifestations of the force in nature which is seen in 
the magnet. 

Magnetic Amplifier—A variable impedance connected in Bhunt with the 
external circuit of the Alexanderson Alternator for control of 
signalling. 

Magnetizing Current—The current which flows in the primary winding 
of a transformer when the secondary has “no load” or an “open 
circuit. 


204 


RADIO THEORY SIMPLIFIED 


Magneto—A small alternating current generator using permanent field 
magneis. 

Magnet, Electro—A magnet formed by passing an electric current through 
a selenoid or a coil of wire. 

Manganise Dioxide—An oxygen giving substance used to prevent polar¬ 
ization in sal ammoniac batteries, such as dry cells. 

Manganin—An alloy used as a resistance in laboratory units. 

Mass of Electron—The electron represents the smallest known compo¬ 
nent of matter, its weight being about one two-thousandth that of 
the hydrogen atom. 

Mass Resistivity—The resistivity of a mas3 of a substance rather than 
of its volume. 

Masts—Supporting towers for radio antenna. 

Mechanical Rectifier—A device for rectifying alternating current by 
mechanical means. 

Megohm—A resistance of 1,000,000 ohms. 

Meter—The metric unit of length, equivalent to 39.37 inches. An instru¬ 
ment for measuring quantities of length. 

Meter-Amperes—A factor in indicating the radiating strength of radio 
transmitting stations. 

Metric System—A system of weights and measures originating in France. 

Mho—The unit of conductivity or the reciprocal of resistivity. (See 
Conductivity). 

Mica—An insulating material having a dielectric constant of four to 
eight and a dielectric strength of from 700 to 1500 volts per 
mil. 

Microfarad—The one millionth part of the farad which is the practical 
unit of capacity. 

Microhenry—A millionth of a Henry, the practical unit of inductance. 

Microhm—A millionth of an ohm. 

Micro-microfarad—A millionth of a microfarad. 

Microphone—A device by means of which sound vibrations cause corres¬ 
ponding variations of an electric current. 

Mil—A unit of length used in measuring the diameter of wires. It 
is equal to one thousandth of an inch. (See Circular Mil). 

Milliammeter—An instrument for measuring small currents. 

Millihenry—One thousandth of a Henry. 

Millimeter—A metric measure of length, one tenth of a centimeter and 
equivalent to .03937 inch. 


RADIO THEORY SIMPLIFIED 


205 


Millivoltmeter—An instrument for measuring small differences in po¬ 
tential. 

Modulated waves—Alternating current waves which have their amplitude 
varied periodically. 

Modulating Action—The action where a radio frequency wave is modulated 
by an audio frequency wave. 

Modulation—The act of varying the amplitude of radio frequency oscil¬ 
lations by the action of the audio frequency changes established by 
the transmitter. 

Absorption method where the radio frequency output of an electron 
tube is absorbed to an extent which varies from instant to instant 
by the use of a second tube. 

Modulation Frequency Ratio—The ratio of modulation frequency to wave 
frequency. 

Modulator—The device used for the purpose of modulating the alter¬ 
nating current wave. 

Molybdenite—A mineral used in a crystal detector. 

Moorehead Tube—A type of electron tube made by the Moorehead Labor¬ 
atories. 

Morse Code—A system of dots and dashes for signalling and used by the 
land telegraph companies. 

Motion, Wave—Wave motion is the phenomena of the progression of 
a shape or condition. It is the oscillation to and fro of the parts, 
or particles, of the medium about their respective equilibrium positions. 

Motor—An electrical machine for converting electrical energy into me¬ 
chanical energy. 

Motor-Generator—A motor and generator connected so as to deliver elec¬ 
trical energy of the desired kind. 

Multiple Tuned Antenna—One with connections through inductances to 
ground at more than one point and so determined that the total 
reactances in parallel are equal to those necessary to give the an¬ 
tenna the desired natural frequency. 

Multiplex Telegraphy—The transmission of several messages over the 
same wire without one interfering with another. 

Multipolar Machine—An electric machine having several pairs of field 
poles. 

Mutual Inductance—The term applied to designate the inductance pro¬ 
duced by a current change in one of two independent circuits which 
react upon each other. 


206 


RADIO THEORY SIMPLIFIED 


N 


National Electrical Code—See Fire Underwriters. 

Natural Frequency— The frequency of the oscillations that take place in 
a circuit of inductance, capacity, and resistance. 

Natural Magnet—The black oxide of iron found in the earth called 
magnetite and having strong magnetic properties. 

Natural Period—The period of the free oscillatory discharge of a con¬ 
denser thru an inductance. 

Negative Electricity—Supposedly those charges of electricity which are 
called electrons. 

Non-Conductors—Those substances which do not ordinarily conduct elec¬ 
tricity. 

Non-Synchronous Gap—A rotating spark gap which runs without regard 
to the generator speed. 


O 


Ohm—The practical unit of resistance. The resistance that will allow 
one ampere of current to pass under the pressure due to an electro¬ 
motive force of one volt. 

Ohm's Law—The relation between the current, electromotive force and 
resistance: 

Amperes = Volts divided by Ohms. 

Volts = Product of Amperes and Ohms. 

Ohms = volts divided by Amperes. 

Oil Cooled Transformer—One in which the windings are immersed in 
oil for the purpose of dissipating the heat loss. 

Open-Core Transformer—A transformer having the path of the magnetic 
flux partly through air. 

Operators License—See License. 

Ordinate Axis of—One of the elements by which a point is referred 
to a system of rectilinear axes. 


RADIO THEORY SIMPLIFIED 207 

Oscillator, Hertzian—An apparatus for generating electromagnetic 
waves. 

Oscillator, Tube—The electron tube made to generate high frequency 
currents by proper adjustment of the electrical constants. 

Osdllion—A type of electron tube made by the DeForest Telephone and 
Telegraph Company. 

Oscillations—Alternating currents of high frequency. 

Oscillation Transformer—An open type of transformer primarily used 
for transferring oscillating energy from one circuit to another. 

Oscillatory Circuit—A circuit of capacity and inductance in which oscil¬ 
lations occur. 

Overmodulation—The distortion of speech caused by too great variation 
of the amplitude., of the modulating audio frequency. 

Oxide Coatings—The coatings of the filaments of some electron tubes 
by the oxides of barium, calcium, or thorium to cause greater elec¬ 
tron emission. 


P 


Pancake Oscillation Transformer—A type of transformer having flat 
spiral windings. 

Panel—A sheet of insulating material on which electrical apparatus is 
mounted. 

Paper, Dielectric Constant of—Dry paper has a dielectric constant of 
1.5 to 3. 

Paraffine—A crude oil derivative having good insulating qualities and a 
dielectric constant of 2 to 3. 

Parallel Connection—A connection in which the current divides, only 
a part of the total current passing through each device. 

Parallel Connection of Resistance—An arrangement whereby a number 
of conductors connect the same two points. From this the total 
resistance is; the sum of the reciprocals of the separate resistance 
in parallel is equal to the reciprocal of the resultant resistance. 

Parallel Connection of Condensers—An arrangement whereby a number 
of capacities connect the same two points. Since the capacity is 
proportional to the plate area and parallel connection simply in¬ 
creases the area, the total capacity is equal to the sum of the separate 
capacities. C-C—C—S, etc. 


208 


RADIO THEORY SIMPLIFIED 


Parallel Resonance—A condition existing when a circuit of lumped ca¬ 
pacity and lumped inductance are connected in parallel to a source 
of alternating E. M. F. and so adjusted that the current supplied by the 
source is a minimum. 

P ea k—The point or points of maximum amplitude on a resonance curve. 

Peanut Audion—A name given to the smaller sizes of electron tubes. 

Perikon Detector—A type of crystal detector using bornite and zincite in 
contact. 

Period—The time required for one cycle. 

Permeability-Magnetic—The ratio of the induction to the magnetizing 
force in a substance. 

Permanent Contact Crystal Detector—A detector which does not require 
adjustment. 

Phase—An aspect or appearance occurring at the same definite pai*t of 
each succeeding cycle. 

Phase Difference—The difference in position in the cycle usually expressed 
as an angle. 

Phenolic Insulating Materials—A type of insulating materials, one of 
which is bakelite. 

Phosphor-Bronze—An alloy of high tensile strength and often used as 
antenna wire. 

Plate—The plate-like electrode in a vacuum tube which collects the elec¬ 
trons emitted by the filament. 

Plate Battery—The source of E. M. F. connected in the plate circuit to 
give the plate element its positive charge. 

Plate Circuit—That part of the vacuum tube circuit including all the 
devices connected directly in the circuit between the filament and the 
plate elements. 

Plate Current—The current passing between the plate and heated cathode 
or filament, in an electron tube. 

Plate Resistance—See Internal Output Resistance. 

Plate Modulation—Modulation by variation of the input plate power. 

Plate Voltage—The potential given the plate of the electron tube by the 
plate voltage supply. 

Pliotron—A type of electron tube designated for transmitting purposes. 

Polarization—The formation of a film of hydrogen gas on the positive 
plate of certain primary cells which tends to reduce the current 
flow. 

Poles, Battery—The terminals of batteries to which the external circuit 
is connected. 


RADIO THEORY SIMPLIFIED 


209 


Poles, Magnetic—The points at which magnetic lines of foree appear 
to enter. 

Positive Electricity—The condition of the atom which has lost some of 
its electrons. 

Potentiometer—An arrangement for securing any desired voltage by 
utilizing the voltage drop across a portion of a current carrying 
resistance. 

Power Factor—The ratio of the true watts to the apparent watts or 
voltamperes of an alternating current circuit. The cosine of the 
angle of lead or lag of the current with reference to the E. M. F. 

Power Factor Indicator—An instrument to indicate the power factor 
of a circuit. 

Primary Cell—A type of cell whose voltage is directly due to the chemical 
decomposition of matter. 

Primary Coil—The coil of a transformer that is electrically connected 
to the source of energy. 

Pulsating Current—A periodic current the average value of which is not 
zero. A pulsating current is the sum of an alternating and a direct 
current. 


0 

Quadrature—Expressing a phase difference of 90 degrees (90°). 

Quarter Phase—Also two phase. The combination of two alternating 
current circuits differing in phase by 90° or a quarter of a cycle. 

Quenched Gap—A gap so arranged that the spark is quenched quickly 
by a cooling effect. A method used to give impulse excitation. 


R 

Radiation—The emission of energy from a source—as of electromagnetic 
waves from an antenna. 

Radiation Efficiency—Of an antenna &t a given wavo length is the 
ratio of power radiated to the total power delivered to the antenna. 


210 


RADIO THEORY SIMPLIFIED 


Radiation Resistance—A fictitious term applying to the power output 
of an antenna, which in considered as being a resistance los3. It 
represents the real useful output of the antenna. 

Radio Communication—The science of transmitting and recording knowl¬ 
edge by means of radio. 

Radio Compass—The name applied to a type of receiving apparatus used 
for taking direction bearings. 

Radiocast—See Broadcast. 

Radio Frequency—Currents considered as having a frequency of 10,000 
cycles or more. 

Radio Frequency Amplifier—An amplifier in which the signals are am¬ 
plified before reaching the detector. 

Radiogoniometer—The direction finder. 

Radiogram—A telegram sent by radio. 

Radiophone (Verb)—To transmit speech by radio. 

Radiotelephony—The science of transmitting speech by means of radio. 

Radio Wares—The electromagnetic waves produced by an oscillatory dis¬ 
charge and which move at right angles to the line of propagating 
with the speed of light. 

Radiotron—The trade name given electron tubes used for receiving purposes, 
distributed by the Radio Corporation of America. 

Ratio of Transformation—The ratio of the induced E. M. F. of the 
secondary to the E. M. F. impressed on the primary. 

Reactance—The opposition offered to the flow of an alternating current 
which is due to the presence of inductance or capacity or both, in 
the circuit. 

Reactance Coil—See Choke Coil. 

Reactance Factor—The ratio existing between the reaction of a circuit 
and its ohmic resistance. 

Reactive Drop—The drop in potential caused by reactance as distinguished 
from that caused by ohmic resistance. 

Reactive Factor—The ratio of the wattless volt-amperes to the total 
volt-amperes. 

Reactor—See Choke Coil. 

Receiver, Telephone—A device by means of which the variations in the 
electric current reproduce the corresponding sounds. 

Receiving Apparatus—All the associated apparatus used for receiving 
and rectifying radio waves. 

Reception, Beat—See Beat Reception. 


RADIO THEORY SIMPLIFIED 


211 


Reciprocal—Unity divided by quantity. Multiplying by the reciprocal 
of a number is equivalent to dividing by the number. 

Rectifier—Any device for converting alternating current into direct or 
pulsating current. 

Regenerative Circuit—An electron tube circuit in which additional am¬ 
plification is produced by feeding back some of the energy of the 
plate circuit into the grid circuit. 

Re-ignition—Starting the arc by the oscillating current in the direction 
opposite to the steady current after it has been extinguished by 
the oscillatory current. 

Rejector—A supplementary closed resonant circuit, consisting of a low 
resistance inductance and a condenser and tuned to the frequency 
of the desired signal, connected as a loop in shunt across the re¬ 
ceiving primary circuit and acting to provide a low impedance by¬ 
pass for all frequencies except that of the desired signal. (Some¬ 
times called a “shunt trap.”). 

Relay—A device actuated by an electric current to open or close another 
circuit. 

Remote Control—Controlling a radio station from a distant point. 

Repulsion Motor—An alternating current motor deriving its power from 
the mutual repulsion between armature and field. 

Resistance—The opposition to the passage of an electric current by any 
substance or material. The unit is the ohm. 

Resistivity—The measure of the resistance of a material to the flow of 
electricity. 

Resistance Coupling—The coupling between two circuits when they 
have a resistance in common. 

Resistance, Effective—As applied to high frequencies, it is the power 
lost in heating or otherwise dissipated, divided by the square of 
the effective current. 

Resistance, Radiation—See Radiation Resistance. 

Resistance, Internal Input of Electron Tube—The ratio of voltage change 
to current change, the grid voltage being constant. 

Resistances, Series Connection—An arrangement of conductors whereby 
the total resistance is equal to the sum of the resistance. 

Resistance, Parallel Connection_See Parallel Connection of resistances. 

Resonance—The condition that exists when the effects of the capacity 
and inductance of a circuit are balanced. 

Resonance Curve—A curve which shows the change of current in a cir¬ 
cuit, when changes are made which cause the resonance condition to 
be somewhat departed from. 


212 


RADIO THEORY SIMPLIFIED 


Resonance Frequency—The frequency which makes the capacitive and 
inductive reactances equal. 

Rheostat—A resistance device, usually variable. 

Right Hand Rule—A rule for indicating the direction of magnetic effect. 
Grasp the wire with the right hand and with the thumb extended 
along the wire in the direction of current. The curved finger tips 
will indicate the direction of the magnetic effect. 

Ring Winding—A name given to type of armature winding. 

R. M. S.—Abbreviation of root-mean-square. 

Root-Mean-Square Value—The square root of the mean square of an 
alternating current or electromotive force. Also called effective 
value or virtual value. The root mean square value of sine wave 
is .707 times the maximum value. 

Rotary Converter—See Synchronous Converter. 

Rotary Gap—A revolving spark gap. 

Rotary Phase Converter—A machine which converts an alternating 
current to a different number of phases without change of fre¬ 
quency. 

Rotating Magnetic Field—A magnetic field created by polyphase current 
circulating in properly distributed windings which steadily and per¬ 
iodically advance the polarity of the different parts of the mag¬ 
netic field. 

Rotor—The rotating part of a motor, generator or other electrical machine. 


S 


Sal Ammoniac—A compound (ammonia chloride) used in solution as the 
electrolyte in certain primary batteries. 

Saturation, Electron Tube—The condition existing when the space charge 
caused by the large number of negative electrons in the tube 
fully counteracts the influence of the positive charges on grid and 
plate. 

Scale—A series of dimensions arranged to give numerical readings of 
the setting of the device to which it is connected. 

Scott Connection—A method of connecting transformers to change from 
three to two phase oar the never ee. 


RADIO THEORY SIMPLIFIED 


213 


Secondary Battery—A class of chemical electric generator which can 

be recharged. Storage batteries fall in this class. 

Secondary Coil—The coil in which electromotive forces are induced. 

Secondary Emission—Electron emission in which the exciting agency 
is bombardment of the emitting material by the electrons. 

Self-Inductance—The property of an electrical circuit which tends to 
prevent any change in the current established in the conductor. 

Self-Heterodyne—A system for receiving continuous wave signals by the 
production of audio frequency beats, through the use of a device 
which is both a radio frequency generator and a detector of the 
audio frequency beat currents produced. 

Sending Station—One equipped with apparatus for producing and ra¬ 
diating radio messages. 

Separate Heterodyne—The securing of beat notes by use of a separate 
source of oscillations. 

Series Condenser, Antenna—When a condenser is connected in series with 
an antenna the condition of series condensers exists and the wave 
length of the antenna circuit is reduced. 

Series Connection—A connection of electrical apparatus or circuits in 
which all of the current passes through each of the devices in suc¬ 
cession, or one after the other. 

Series Connection of Condensers—An arrangement of capacities wherein 
the same charge is given to each condenser and the total voltage 
is subdivided among the condensers in direct ratio to their capaci¬ 
ties. 

Series Motor—An electric motor in which the armature and field windings 
are connected in series. 

Series Resistance—See Resistance, Series Connection. 

Series Resonance—When a single lumped capacity and a single lumped 
inductance are connected in series between terminals to which an 
alternating E. M. F. is applied and the inductance oi capacity or 
frequency is varied, the condition of series resonance exists when 
the current is maximum. 

Shape Factor—A numerical quantity in formulae for the calculation of 
the inductance of coils. 

Sharp Tuning—Refers to the generation of a fundamental of a pure 
wave, in which practically no harmonics are present. This is de¬ 
sirable to allow freedom from interference. 

Sharpness of Resources—A quantity expressing the fractional changes of 
current in a simple series circuit for a given fractional change in 
either capacitive or inductive reactance at resonance. 


214 


RADIO THEORY SIMPLIFIED 


Sharp Wave—A “pure wave” or one which has energy at or near only 
one wave length—as indicated by a “sharp” resonance curve. 

Shellac—A material used for insulating and binding purposes, having 
a dielectric constant of from 3 to 3.7. 

Shell Transformer—A transformer having the primary and secondary 
coils within the iron shell which constitutes the magnetic circuit. 

Shunt Circuit—An arrangement of apparatus or circuits in which the 
total current is subdivided. 

Shunt Winding—The arrangement of windings of motors or generators 
where they are connected in shunt. 

Side Frequency—The frequency of the side waves. 

Side Waves—See Band, Wave Length. 

Silicon—One of the metallic elements used for detecting purposes. 

Silicon Steel—Steel containing a small amount of silicon and highly 
desirable for its magnetic properties. 

Silver Chloride Cell—A type of dry cell in which the depolorizer is 
silver chloride and in which the positive electrode is silver and the 
negative zinc. 

Simple Alternating Current—A sine wave. 

Sine Curve—See Curve Sine. 

Single Layer Coil—A coil having all turns side by side and in only one 
layer. 

Single Phase—An alternating current system in which only two wires 
are necessary and making use of only one E. M. F. 

Single Phase Alternator—A generator of single phase electromotive 
forces. 

Sinusoidal—Having characteristics that can be represented by a sine 
curve. 

Skin Effect—The tendency of an alternating current to pass through the 
outer portion rather than through the center of a conductor. 

Slip of Induction Motor—The difference in the number of revolutions 
made by a revolving field and the rotor of the motor. 

Solder—An alloy of lead and tin having a low melting point. 

Soft Tube—A vacuum tube having a lesser degree of vacuum than that 
of the hard tube. 

Solenoid—A coil consisting of a number of turns in cylindrical form. 

Sound Waves—The waves given off by a vibrating body which are trans¬ 
mitted by an elastic material medium and which can be perceived 
by the ear. 

Spark—An arc of very short duration. 


RADIO THEORY SIMPLIFIED 


215 


Spark Frequency—The number of sparks that occur per second. 

Spark Gap—Terminals or electrodes designed to permit spark discharges 
to take place across a gap. 

Specific Gravity—The weight of a material in proportion to the weight 
of an equal volume of water. 

Specific Inductive Capacity—The direct measure of the ability of a 
substance to store up electrical energy when used as a dielectric 
material in a condenser. 

Spider Web Coil—A special type of stagger wound or open weave flat 
inductance coil which haa low distributed capacity and high effi¬ 
ciency. 

Spiral Oscillation Transformer—See Pancake Oscillation Transformer. 

Split Phase—A difference in phase resulting usually from an unequal 
distribution of reactance in different branches of a divided single 
phase circuit. 

Stagger-Wound Inductance Coil—A type of inductance coil which has its 
layers staggered with reference to each other—as in the duo-lateral 
coil, or its turns staggered—as in the spider web coil. 

Standards, Bureau of—A Bureau of the government established for the 
purpose of scientific investigation. 

Standard Cell—A type of cell which has a steady or standard E. M. F. 
(See Cadmium Cell). 

Star Connector—The connection of the three windings of a three-phase 
system in the form of a star. Also called “Y” connection. 

Star Delta Connection—The designation of the connection of the primary 
windings of a bank of transformers in star and the secondary 
windings in delta. 

Static—Conduction or charging current in the antenna system resulting 
from physical contact between the antenna and charged bodies or 
masses of gas. 

Static Electricity—Defined as electricity at rest, in contradistinction to 
current electricity. (See Frictional Electricity.) 

Station License—A permit to operate a transmitting station granted by 
the government. 

Stator—That part of an electrical machine or device which remains 
fixed. 

Step-Down Transformer—A transformer wound to give a lower voltage 
on the secondary side than that impressed on the primary. 

Storage Cell—A type of cell in which the chemical changes of dis¬ 
charge may be reversed by application of an electric current to 
charge it. 


216 


RADIO THEORY SIMPLIFIED 


Strays—Disturbances in radio reception due to electromagnetic fields 
other than those caused by radio transmitting stations, caused 
by sparking commutators, sparks on trolley lines, controllers, igni¬ 
tion systems, etc. 

Sulphation—The formation of lead sulphate on the plates of the lead 
acid cell. It results in harm to the cell and i3 particularly harmful 
if the cell is left in an uncharged condition. 

Super Heterodyne—A type of radio receiver operating on the heterodyne 
or beat principle. 

Surface Leakage—The loss of current due to a conducting film on in¬ 
sulators. 

Susceptance—The reciprocal of reactance. The unit is the mho. 

Synchronizer—An instrument used for indicating the phase relation of two 
alternating current machines. 

Synchronous—Simultaneous. Occurring at the same time. 

Synchronous Alternator—An alternating current generator operating or 
capable of being operated in synchronism with another generator. 

Synchronous Converter—A rotating machine having a field excited by 
direct current and an armature connected to a commutator and a set 
of collector rings, used to convert direct to alternating or the reverse. 

Synchronous Motor—A machine constructed similar to a separately ex¬ 
cited alternator but operated as a motor. 


T 


Telegraph Key—A type of switch for making and breaking a circuit at 
will for the purpose of transmitting dots and dashes. 

Telephone Receiver—A device for producing sound impulses from electric 
current variations or vice versa. 

Telephone Transmitter—Refers strictly to a device for converting sound 
pulsations into electric current variations. 

Tesla Coil—A special type of step-up transformer used primarily to produce 
very high voltages. 

Thermal Ammeters—Current measuring instruments that operate due to 
the heating effect of an electric current. 

Thermo Couple—A junction of two different metals which develop an E. M. 
F. when heated. Used with ammeters to measure small currents. 


RADIO THEORY SIMPLIFIED 


217 


Thermoelectricity—The electrical energy which is transformed from heat 
energy in the thermo couple. 

Three-Electrode Tube—A combination of a heated cathode, a relatively cold 
anode, and a third electrode for controlling the current flowing between 
the other two; the whole enclosed in an evacuated bulb. Variously 
called, audion, pliotron, radiotron, oscillion, audiotron, aerotron, 
electron tube, vacuum tube, etc. 

Three Phase—Having three electromotive forces with a phase displacement 
of 120° between them. 

Tickler—The coil in the plate circuit used to feed some of the energy back 
into the grid circuit. (See Feed Back). 

Tikker—A device for rapidly and somewhat irregularly making and break¬ 
ing the circuit of a receiver for reception of undamped waves. 

Time Constant—Refers to the rate of building up the charge in a condenser. 
The larger the capacity and resistance, the longer the time required. 
The product CR is called the time constant. 

Time Signals—Signals transmitted each day for indication of correct time 
by certain radio stations. 

Tone Modulation—The chopper, buzzer and sine-wave modulation system 
are referred to as “tone modulation.” 

Torque—The amount of force which tends to produce rotation of the arma¬ 
ture of a motor or other source of power. The unit is the pounds-foot 
or pounds-inch. 

Train Frequency—The number of groups or trains of waves per second. 

Trains, Wave—Groups of alternating current waves of both the continuous 
and discontinuous type. 

Transformer—A device for transferring energy from one circuit to another. 

Transmission, Radio—The propagation of electromagnetic waves from a 
transmitting station. 

Transmitter—See Telephone Transmitter. 

Transmitting Antenna—An arrangement of conductors connected to a gen¬ 
erator of high frequency currents for the radiation of radio waves. 

Transmitting Circuit—The arrangement of and connections to pieces of 
apparatus used in the generation of currents of high frequency for 
radio transmission. 

Tube, Electron—See Three Electrode Tube. 

Tuned Circuit—A circuit having its value of capacity and inductance such 
that the period of vibration corresponds to a desired value. 

Tungar Rectifier—A device for changing alternating to direct current, 
working in the electron flow principle. 


218 


RADIO THEORY SIMPLIFIED 


Two Electrode Electron Tube—A vacuum tube having a hot cathode and a 
relatively cold anode, or one with filament and plate only. 

Two Phase Alternator—A machine for generating two phase alternating 
electromotive forces. 

“T” Type Antenna—A flat top antenna in which the lead-in is taken 
from the center of the horizontal portion. 


U 


Umbrella Type Antenna—An antenna the conductors of which form el- 
ments of a core with the apex at the top, to which the lead-in is 
connected. 

Undamped Alternating Current—A current passing through successive 
equal cycles of time whose average value is zero. 

Undamped Waves, Radio—Waves representing a true alternating current. 
Those of constant amplitude and called continuous waves. (See 
Continuous Waves). 

Underground Antenna—An antenna consisting of an insulated wire and 
placed a short distance under the surface of the ground. 



Vacuum Tube—See Electron Tube. 

Variable Condenser—One whose electrical capacity may be changed or 
varied. 

Variable Inductor—A name sometimes applied to a variometer. 

Variation, Wave Length for Modulation—The variation of wave length to 
produce modulation by using a voice controlled variable condenser. 

Vario-Coupler—An arrangement of two or more coils so that the movement 
of the coils will vary the coupling. 

Variometer—A variable inductance controlled by altering the relative 
position of two coils. 

Vector—A quantity having both direction and magnitude. 

Velocity—The distance traveled by a wave in one second. For the electro¬ 
magnetic wave it is 186,300 miles per second. 


RADIO THEORY SIMPLIFIED 


219 


Vernier Condenser—A condenser having small capacity changes. 

Voice Modulation—The variation of amplitude of an alternating current 
wave by means of the voice. 

Volt—The unit of electromotive force. The electrical pressure required 
to send a current of one ampere through a resistance of one ohm. 

Voltage Amplification—The ratio of the voltage change produced in the 
output apparatus in the plate circuit to the change in the voltage 
impressed on the grid. 

Voltmeter—A device for measuring the difference of potential in volts. 

Voltage Drop in Generator or Battery—See Internal Drop. 

Vulcanized Fibre—An insulating material having a dielectric constant of 
from 5 to 8. 

“V” Type Antenna—Two sets of horizontal wires supported by three masts 
so that the horizontal portions form an angle. 


W 

% 

Water Pipe Ground—A water pipe to which connection is made for the 
ground. 

Water Rheostat—A rheostat which uses the resistance properties of water 
or some salt in solution. 

Watt—The unit of electrical power and representing the product of current 
and electromotive force. 

Wave Antenna—A horizontal antenna the physical length of which is 
approximately equal to the length of signaling waves to be received, 
and which is used so as to be directional. 

Wave Changer—A transmitting device for rapidly changing the radiated 
wave length. 

Waves, Continuous—See Continuous Waves. 

Wave, Damped—See Damped Wave. 

Wave Distortion—Divergence from a sine wave. 

Wavemeter—A radio instrument for measuring frequency. 

Wave, Sine—See Sine Wave. 

Wave Train—See Trains, Wave. 

Wave, Undamped—See Undamped Wave. 

Weston Cell—See Cadmium Cell and Standard Cell. 

Wheatsone Bridge—An instrument for measuring resistances. 


220 


RADIO THEORY SIMPLIFIED 


Wired Radio—The guidance of electromagnetic wave* of high frequency 
by conductors. 

Wire Telephony—The transmission of speech over wires. 

Wood’s Metal—An alloy having a low malting point used for mounting 
crystals for detector purposes. 


X 


“X”*—A term sometimes used to designate static, strays, atmospherics, etc. 
X-ray—The radiation produced outside the cathode ray tube which has the 
ability to penetrate materials of considerable thickness. Also called 
Roentgen Rays. 



‘Y” Connection—Same as Star Connection. 

Yoke, Dynamo—The frame from which the poles project radially inward. 


Z 


Zero Beat Reception—Also called “homodyne” reception. A method of 
reception using a radio frequency current of the proper magnitude and 
phase relation so that the voltage impressed on the detector will be 
of the same nature as that of the wave. 

Zincite—A mineral (natural red oxide of zinc) used as a detector material. 

Zinc Spark Gap—A spark gap having zinc as the electrode. 























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